What the mod does:

What's new in this mod

Reworked Roman units
Rebalanced all Roman units stats/equipment in conformity with the reforms
Reworked Roman army caps to allow proper reclutement of Legionary/Cohort troops
Reworked abilities of Roman units: added Repel Cavarly, Form Square, Throw Pila as standard formations plus Scutum Wall (the old Cycled Line) for Legionaries/Cohorts
Reworked all Auxiliaries troops to have Roman formations along their unique capabilities
Redistributed/reworked abilities
Normal sword infantry has now an ability called "To the Death" (the old Rapid Advance) that increases charge and strike power in view of collision with an enemy
Normal spear infantry has the old Pike Square ability
Greek troops have the unique Shield Wall now
Hoplite troops have the unique Hoplite Phalanx plus an ability called "Quick March" that allows them to move faster for a moderate amount of time
Pike troops have the usual Pike Phalanx plus an ability called "Hold the Line" that helps them on holding the ground better by increasing morale and defense
Barbarian spears have now an ability called "Harden Yourself" that increases defense/armor at the expense of attack, plus they now have Frenzy
Created ability called "Throw Javelin" for all melee troops that can use them. With it you can throw Javelins in self-defense by aiming to the direction enemy troops are
The old "Killing Spree" has become "Intense Attack": revisited a little the bonuses but all in all it's the same ability with new name and icon (to render better the meaning)
Revisited all invalid abilities behaviors for better use of all abilities (for example you cannot use "To the Death!" while near an enemy since it is a charge ability)

Improved behavior of troops
Pike units will now properly always carry pikes and switch to swords when in melee fight.
Changed Scutum Wall (old Cycled Line) behavior to be more consistent and to be the only formation that can oppose an Hoplite Phalanx with elite troops (as Eagle Cohorts)
Removed formation behavior from poorly trained spear infantry
Added ability to fire while hidden for Longbow Hunters
Increased vertical spacing for more realism
Increased run speed of heavy/very heavy infantry so that they don't "jog" instead of running
Revisited run speeds of cavalry in general
Improved unit cohesion once more by slightly increasing mass on melee infantry and tweaking some factors
Abilities localization
Added add-on for users using localized version of AGA so that for now at last they can have the correct abilities descriptions in english in view of the future translations
NOTE: Sadly for a limitation of the engine you cannot use Throw Javelin/Pila ability while in a formation, so you must be sure to disable the formation before you use the ability
Overview of the changes:
Battle dynamics (fatigue, morale, speed of battle, speed of units) overhaul. The battles will be more realistic, units will move truer to real life responding to fatigue in believable ways and you will see the difference between disciplined units and those that are not, with either certain characteristics tied specifically to some particular units to make them even more unique.
Units size, stats and behavior overhaul. Every unit type will now have a precise role in the battlefield and stats/equipment tied to that role. Also tweaked are certain unit sizes for better balance on the battlefield.
Factions overhaul. Factions will be completely unique in Ars Gratia Artis and they will dictate which type of abilities units have and the way they behave. Factions will also have unique strength/weaknesses and unique number of armies they can field in the battle. 
Equipment (weapons, armors, projectiles etc.) overhaul. All armors and weapon types have been completely reworked for a more balanced experience. Also weapons and armours, as units, will have a precise role on what they are best at.
Abilities overhaul. Reworked all special abilities in the game to be more realistic. Now they play a strong role on render every faction unique and make the General experience more important.
Improved visuals (optional). Some of the best re-textures and visual modifications are included in the mod for the best experience possible because also the eye wants its part.
Changes in the specific:
Battle dynamics (fatigue, morale, speed of battle, speed of units) overhaul
The battle speed now is more realistic and enables tactical play. All units have their proper role and group fight and experience makes much more of an impact on morale of units. Fatigue is a great component of the battle for it greatly decrease the ability to fight, so reserves are dramatically important now. All units have hand-tailored speeds by type, with Pike infantry being the slowest followed by spears, sword and cavalry and barbarian units are faster.
- Units will tire more easily than before but the steps are less abrupt.
- Units will now recover from fatigue faster when idle enhancing the role of backups.
- Greatly increased and added penalties to fatigue thresholds so that they have much more of an impact on combat ability of units. 
- Increased base morale of units and increased morale received by experience.
- Rout figure of units reworked to be less abrupt.
- Increased morale impact by having friendly units around.
- Decreased morale by having missile fires incoming.
- Increased impact of flanking and rear attacks on morale.
- Disciplined and civilized units will keep formations steadly.
- Barbarian units will not keep any formation and will go through the ranks.
- Improved units spacing for disciplined infantry and cavalry. 
- Created special spacing rules for certain special elite cavalry in selected factions.
- Reworked generally all unit speeds for more realism. 
- Reworked all light horse/infantry speeds for them be a real viable tactical option for the great ability to flank heavier troops.
- Created special speed behavior for all units to evidence better their roles.
- Revisited all speeds for weights of cavalry. 
- Decreased by much turning speed of formations for more realism and also better tactical approach since now flanking is much more of an issue.

Units size, stats and behavior overhaul
All unit types have been reworked to adhere to specific roles so that the user can tactically plan the battle. I also tailored certain unit sizes for better balance and since patch 4, with the possibility of loose spacing working, I inserted the ability to go in loose formation for all units but Romans that have Testudo. Also here unit roles and factions specifics will make a difference because depending on the type of troop the loose line will be more or less large and so more or less resistant to incoming missile damage.
General changes:
- Reworked experience threshold per faction so that experience bonuses per unit are more specific for every faction.
- Increased experience threshold levels. With the changes in the thresholds tied to the increased time to increase experience every faction will have more definite strength/weaknesses. 
- Increased cavalry sizes to 100.
- Increased chariot size to 40 and scythed chariots to 48.
- Increased many units sizes that had no reason to be lower than the 160 standard.
- Updated major factions starting rosters with the changed sizes. I willingly changed the starting rosters only of some factions to help them stand the campaign.
- Added loose spacing to all infantry/cavalry types apart roman units that have Testudo.
- Created different spacings for loose formation so that pikes and spears are more exposed to missile damage even in loose formation.
Roles changes:
Melee Infantry
Sword infantry
Stats: moderate speed, very high attack, moderate defence and high armor. 
Base abilities: shield wall.
Role: sword infantry has the highest attack of all units and it is at its best in a close quarter fight, especially by flanking, just beware of cavalry units doing the same to them.
Spear infantry
Base stats: very low speed, very low melee attack, very high defence and very high armor. 
Base abilities: spear square, rapid advance.
Role: spear infantry is the highest defence and armor unit and it is very strong against cavalry and to repel charges and as such it is a good impact unit.
Pike infantry
Base stats: low speed, moderate melee attack, low defence and low armor (in a phalanx high defence and high armor)
Base abilities: pike phalanx, steady retreat.
Role: pike infantry is an unit very deadly in a phalanx but very weak outside of it. Its very low speed renders the unit very weak to outflanking maneuvers, however the phalanx power renders this particular unit the best first line unit in the game.
Missile Infantry
Bow missile
Base stats: high accuracy, high range, moderate armor penetration.
Base abilities: quick reload, precision shot, flaming arrows.
Role: the bow unit is the bread & butter of missile infantry; with its high range and good accuracy can quickly thin an unit at range if not highly armored. 
Sling missile
Base stats: low accuracy, very high range, very low armor penetration.
Base abilities: precision shot.
Role: the sling unit has a very high range that make it very deadly against low armored units. However against high armored units their efficacy is much lowered.
Javelin missile
Base stats: moderate accuracy, very low range, very high armor penetration.
Base abilities: none.
Role: javelins units are very deadly if they can come close to the targets as their very high armor penetration and damage can make short work of every unit type. Just beware of ammo capability!
Mount units
Sword Cavalry
Base stats: moderate speed, moderate charge, high melee attack, low melee defence, moderate armor.
Base abilities: Fury.
Role: Sword Cavalry is the best cavalry against sword infantry since it can make short work of them in melee. Some units of Sword Cavalry also posses Javelins to make them even more deadly against infantry. Against other types of cavalry, however, sword is the weakest one. 
Spear Cavalry
Base stats: low speed, moderate charge, low melee attack, high melee defence, high armor.
Base abilities: Flying wedge.
Role: Spear Cavalry is the anti-cavalry per excellence since it can make short work of every other cavalry type. Apart this, then, it is also moderately good against sword infantry. 
Shock Cavalry
Base stats: high speed, high charge, moderate melee attack, low melee defence, low armor.
Base abilities: Gallop.
Role: a pure harassing force, Shock Cavalry is the pure hit-and-run unit in the game with immense impact power while gallopping. Some of the best cavalry units in the game are from this category. Outside of their charge, however, Shock cavalry is weak and fragile apart some very special exceptions.
Missile Cavalry
Base stats: high speed, low charge, low armor and defense, moderate accuracy, very high range, moderate armor penetration.
Base abilities: Quick Reload (arrows only), Precision shot.
Role: missile cavalry is one of the best skirmishers given their very high speed and mobility. What they lack in numbers in comparison to missile infantry they get for mobility and full 180 degree arc range. For the rest they have the same weaknesses of missile infantry, included other cavalry.
Elephants
Base stats: low speed, high charge, high melee attack, high melee defence, low armor.
Base abilities: Kill elephants, Stampede.
Role: elephants are a very powerful and can wreak havock against every other unit in the game; their major weakness are pikes/spears and fire, especially the one of javelins for factions having them.
NOTE: Abilities and/or stats and roles can vary greatly depending on the faction. As such it is important to look at these roles only as generic points because in the specific situation of a faction things can change, even dramatically.
Factions overhaul.
All factions have been overhauled to make them all unique and playing with them different. As in history some factions will be ineherently stronger than others for lack of resources or either general unit power, but everyone of them is perfectly strong in their own merits and it also depends on the user to make the most of them. I willingly gave certain factions more power in resources or unit selection because in this is the challenge: if you are weaker it is your duty to win against the odds, and if you are stronger you must know how to use your strength in an effective way to not be crushed. I also did this because newcomers can chose a stronger faction and have an easier journey while users that like a challenge can choose factions that are a little weaker.
Rome Faction
There is not a conglomerate of Roman factions, Rome IS the faction. It being the largest and resourceful of all factions this is not a surprise as Rome has the more disciplined and veteran units, with an advancement in equipment and battle tact is unmatched anywhere else. Units that Rome lacks can be recruited from Auxiliary camps for resources are not a problem for the largest faction in the game. The great power of Rome, completely on the opposite of Barbarians (and in fact when the two met there's a clash of combat styles), is defense: melee infantry units in Rome are the masters in this style and they have all the abilities to supplement this behavior to the most and come out as the winners.
Spoiler Alert, click show to read:   
Army caps
Polybian:
Principes, Socii Extraordinary: 150/120
Triarii: 45
Rorarii: 60
Vigiles: 90
Equites: 90

Marian:
Legionaries: 80
Veteran Legionaries: 55
First Cohort: 15
Legionary Cavalry: 75

Imperial:
Legionary Cohort: 80
Evocati Cohort: 40
Armored Legionaries: 15
Eagle Cohort: 15

Special:
Praetorian: 12 [Depletable]
Praetorian Guard: 8 [Depletable]
Praetorian Cav: 30 [Depletable]
Gladiators: 15 [Depletable]
Gladiator Spears: 15 [Depletable]
War Dogs: 45 [Depletable]

Strengths/Weaknesses
+ Strongest sword infantry unit in the game
+ Very strong sword infantry in its totality 
+ Large selection of very powerful melee units of all types
+ Unique and very powerful Killing Spree ability
+ Unique Pilum
+ Strong Artillery units
- Very weak Cavalry
- No Archer units
- Almost all low speed units.

Unique special abilities
Offensive testudo
Defensive testudo
Shield screen
Killing spree
Hoplite phalanx

Greek Factions
Greek factions are disciplined and strong, with the unique pike units. However, differently from other factions, there are many different approaches in the factions and there is not an unique modus operandi. Egypt is under a dictatorship rule as Eastern factions, Athens relies more on the cavalry, Macedon goes for pure pike unit strength, Carthage has a strong point on the unique Indian Armored Elephants of the generals and the flaming javelins while Sparta relies on their legendary spear units albeit in much smaller numbers than in the times of its glory.
Macedon
Spoiler Alert, click show to read:   
Army cap 
Foot Companions: 60
Royal Peltasts: 45
Shield Bearers: 90
Companion Cav: 60
Aspis Companion Cav: 75
Strengths/Weaknesses 
+ most powerful pike unit in the game 
+ very good melee unit 
+ good shock cavalry 
+ powerful sword cavalry unit
- poor mele outside royal peltasts
- no strong spear cavalry
Unique special abilities 
War Cry
Hoplite Phalanx
Steady Advance
Carthage
Spoiler Alert, click show to read:   
Army cap
Sacred Band: 90
African Pike: 90
Indian Armored Elephants: 15
Strengths/Weaknesses
+ very good spear unit 
+ Armored Elephants usable as Generals
+ more powerful spear units than other factions
+ flaming javelins
- poor selection of cavalry 
- poor selection of sword infantry
Unique special abilities
Flaming Javelins
Hoplite Phalanx
Shield Wall (spear units)
Steady advance

Egypt
Spoiler Alert, click show to read:   
Army cap
Galatian Royal Sword: 30 [Depletable]
Royal Thorax Sword: 45
Royal Peltasts: 45
Galatian Swords: 60 [Depletable]
Hellenic Royal Guard: 60
Ptolemaic Cavalry: 45
African War Elephants: 30
Scythed Chariots: 45

Strengths/Weaknesses 
+ powerful selection of sword infantry with also barbarian units
+ powerful pike unit 
+ strong shock cavalry unit 
+ elephants 
+ poison arrows
+ strong chariot unit
- poor selection of spear infantry units 
- more limited amount of powerful shock cavalry
- poor selection of melee cavalry in general 

Unique special abilities
Use the Whip
Hoplite Phalanx
Steady Advance
Poison Arrows
Headhunt
Frenzy

Sparta
Spoiler Alert, click show to read:   
Army cap
Royal Spartans: 75
Heroes of Sparta: 60 [Depletable]

Strengths/Weaknesses 
+ the most powerful spear units in the game 
+ high morale
+ unique and powerful War Cry ability 
- Sparta is in decadence and as such it has a very limited amount of troops
- very limited troop selection outside of spears

Unique special abilities
War Cry
Hoplite phalanx
Steady advance

Epirus
Spoiler Alert, click show to read:   
Army cap
Hellenic Royal Cav: 60
Hellenic Royal Guard: 60
Aspis Companion Cav: 75

Strengths/Weaknesses
+ strong sword melee cavalry unit
+ strong shock cavalry unit
+ very powerful pike unit 
- poor selection of spear units 
- poor selection of sword infantry units

Unique special abilities
Hoplite Phalanx
Steady advance

Athens
Spoiler Alert, click show to read:   
Army cap 
Hippeus Lancers: 75

Strengths/Weaknesses 
+ powerful shock cavalry unit
+ increased amount of utilizable shock cavalry
- poor selection of pike units 
- limited supply of good sword and spear infantry

Unique special abilities
Hoplite Phalanx
Steady advance

Eastern Factions
The eastern factions are renowned for their powerful cavalry and bow units, capable of destroying by themselves even the strongest resistance. Specific examples under the factions bred the stronger and most powerful horses in all the world and are unmatched by any equal opposition. The Eastern factions are usually under a dictatorship rule and units without noble origin are many times forced to the extreme of their capability to fight, often causing the death of men for too strong exertion. Everything goes to win is the number one motto of these factions and their results demonstrate the point well. 
Parthia
Spoiler Alert, click show to read:   
Army cap
Royal Cataphracts: 30
Cataphracts: 60
Noble Horse Archers: 90
Armor Horse Archers: 120
Noble Blood Cav: 75
Indian War Elephants: 30

Strength/Weaknesses 
+ Cataphracts
+ Powerful units of missile cavalry
+ Strong spear cavalry
+ Elephants
- very weak infantry on the whole

Unique special abilities
Use the whip
Fury (Cataphracts)

Seleucid
Spoiler Alert, click show to read:   
Army cap
Azat Knights: 60
Hellenic Cataphracts: 45
Silver Shield Pike: 60
Silver Shield Sword: 60
Indian Armored Elephants: 15

Strength/Weaknesses 
+ Cataphract unit
+ Very powerful spear cavalry unit
+ Powerful pike unit
+ Strong sword unit
+ Very powerful Armored Elephants
- lacks the missile horse power of other Eastern factions

Unique special abilities
Use the whip
Trample

Pontus
Spoiler Alert, click show to read:   
Army cap
Pontic Royal Cav: 60
Bronze Shield Pike: 60
Noble Blood Cav: 75
Scythed Chariots: 45

Strengths/Weaknesses 
+ powerful blend of eastern and greek units 
+ very good pike unit 
+ extremely good shock cavalry unit
+ good spear cavalry unit 
+ very powerful chariot unit
- very weak infantry as a whole
- lack the missile horse power of other Eastern factions

Unique special abilities
Use the whip
Trample

Barbarian Factions

Barbarians are strong, agile and ruthless. What they lack in discipline they circumvent with pure power and morale. They go ruthless in battle caring little about proper defence because they firmly believe that the stronger defence is attack, and they have the numbers to demonstrate the point. Barbarians are (apart rare exceptions) capable of dishing an insane amount of damage in a short amount of time with a powerful charge an abilities that enhance attack and damage, but this comes at the expense of fatigue and defense. If enemies are able to counteract the first impact barbarians will be in trouble.

Averni
Spoiler Alert, click show to read:   
Army cap
Oathsworn: 150
Noble Horse: 75
Savage Dogs: 30 [Depletable]

Strengths/Weaknesses
+ very strong sword infantry capable of a powerful charge and high damage 
+ unique Headhunt and Frenzy abilities
+ strong spear cavalry unit 
- poor spear infantry 
- undisciplined.

Unique special abilities
Headhunt
Frenzy
Cavalry counter tactics

Cannot use standard units abilities
Shield wall
Spear square
Flying Wedge

Suebi
Spoiler Alert, click show to read:   
Army cap
Sword Masters: 150
Berserkers: 75 [Depletable]
Noble Riders: 75

Strengths/Weaknesses 
+ strong sword infantry capable of a powerful charge and high damage 
+ unique Headhunt and Frenzied Charge abilities
+ special unit with very high charge 
- poor spear infantry 
- undisciplined.

Unique special abilities
Frenzied Charge
Headhunt
Cavalry counter tactics

Cannot use standard units abilities
Shield wall
Spear square
Flying Wedge

Iceni
Spoiler Alert, click show to read:   
Army cap
Heroic Riders: 75
Heroic Nobles: 150
Druid Nobles: 60 [Depletable]
Chariots: 60

Strengths/Weaknesses
+ very strong sword infantry capable of a powerful charge and high damage
+ unique Headhunt and Frenzy abilities
+ special unit that can buff everyone nearby 
+ chariots
- poor spear infantry.

Special abilities
Chant
Headhunt
Frenzy
Cavalry counter tactics

Cannot use standard units abilities
Shield wall
Spear square
Flying Wedge

Equipment overhaul
The changes in this section are very important for the mod because they are the soul of it. The core of the balance resides in the greatly enhanced damage bonuses on weapons and projectiles tied to the completely reworked armor set. The changes render the unit roles more relevant and decrease by much the killing ratio for a much longer combat experience.

- Reworked existent armors in the game for better balance.
- Added many more armor types for better diversification between unit types.
- Reworked weapons base damage and armor penetration to make the armour stat as relevant as defense.
- Overhauled damage bonuses for weapon type so that unit roles are more important.
- Reworked missile damage bonuses and made projectiles types more evident. 
- Tweaked hit roll and general damage for a better experience in battle. Striking from behind or on the flank is more damaging while from the front it is less.
- Created separate weapons for cavalry with different bonuses against infantry/cavalry (melee cavalry vs. infantry, shock cavalry vs. cavalry). 
- Added bonuses vs. infantry to General's bodyguard and Chariots.
- Added to Melee Cavalry, Chariots and Generals an UI bar to know the bonus against infantry.
- Added to Shock Cavalry, Spears and Pikes an UI bar to know the bonus against cavalry.
- Reduced Scorpio Towers damage from vanilla.
- Tweaked Ballista accuracy and damage.
- Reduced Boiling Oil reload time.
- Revisited behavior of all units in the game to be more tied to the faction of appartenence.

Abilities overhaul
All the abilities have been balanced to the changes in the mod and are generally stronger in their effects but also have harsher penalties to go with their use. Every ability has been hand tweaked to work with the unit type it is tied and the role of the same and I removed all instances where there were only strong buffs and no drawbacks. I then especially focused on the fatigue penalties that in vanilla weren't actually penalties at all but on the contrary buffs, since they gave a little penalty to fatigue, yes, but the penalty only lasted for a very little while and in the meantime fatigue froze and when the effect ended you actually saved a lot of fatigue instead than losing it. This made all the fatigue system in the original game completely broken and the various other mods that give harsher penalties to fatigue are worthless without this change.
- Removed cavalry fire arrows. 
- All fatigue penalties in abilities are permanent and will not reset anymore after a while (while in the meantime freezing fatigue generation) as in vanilla.
- Reworked all fatigue penalties to be more consistent with the improved fatigue system and have harsher effects.
- Reworked all forms of Testudo to work effectively in defense but not also for attack, that's what shield wall and screen (especially screen, also if you cannot move) are for.
- Reworked Shield Wall and Hoplite Phalanx to work also when attacking and have the AI able to use them.
- Hoplite Phalanx, Testudo (offensive) and Shield Wall will continue the current action while adopting the new formation. 
- Separated Hoplite Phalanx and Shield Screen bonuses that in vanilla where the same. 
- Changed bonuses on Hoplite Phalanx, Pike/Spear Square and Pike/Spear Wall by increasing bonus against cavalry but decreasing movement speed further. 
- Removed both Diamond and Wedge formations because they were too long and didn't behave correctly.
- Changed Flying Wedge cavalry formation to be a spear cavalry specific formation.
- Reworked Trample to Gallop: it is now a toggle for Shock Cavalry increasing hit-and-run capability by much.
- Improved Battle Rhythm behavior and increased penalties when the effect ends.
- Headhunt now properly scales penalties during the different phases. 
- Reworked Draco to an ability called Fury that increases strike power of Sword Cavalry against infantry.
- Reworked Screech to Intimidating Presence that greatly reduces weapon damage on every unit nearby.
- Reworked Chant ability to work as a toggle and increased its bonuses. 
- Reworked Use the Whip: now it increases for a long time melee attack, damage, reload speed and movement speed but at the cost of extreme fatigue and unit reduction.
- Reworked Steady Advance to be an ability focused against enemy charges by increasing speed, bracing impact and charge bonus, all at the cost of exertion.
- Reworked Frenzied Charge (cavalry) to Trample that increases charge and strike bonus of cavalry.
- Reworked Steady Retreat to be an ability that enables the unit to quickly retreats on the rank by hugely increasing melee defense and speed at the expense of zero attack potential.
- Reworked Frenzied Charge (infantry) to simulate a ruthless charge: the charge bonus is high but there's a penalty to bracing so it's a risky ability against high charge units, as shock cavalry.
- Reworked Killing Spree to be a specific ability used by Evocati/First/Eagle Cohort and Gladiators and greatly increasing strike power of those units.
- Reworked War Cry to be an unique ability of Spartans greatly decreasing damage of enemy units.
- Reworked all General/Commander abilities to have an effect in a radius and increasing the duration of their effects 
- Greatly increased the cooldowns of the General/Commander abilities so you users cannot spam them and must beware when to effectively use them.
- Reworked Second Wind to simulates an adrenaline surge by greatly lowering fatigue but then causing great exertion at the end of the effect.
- Increased fatigue penalty to Use the Whip, Killing spree, Steady advance and Steady retreat. 
- Added a reload penalty on Precison Shot, Flame Arrows and Poison Arrows. 
- Added fatigue penalty to Trample, Stampede, Quick Reload, Rapid advance. 
- Added accuracy penalty to Quick Reload.
- Tweaked bonuses on all abilities for better balance.

Improved visuals (optional)
A full host of visual improvements coming from the best mods out there. Full credits to the authors that created them, I just inserted them here for users so they can have a full pack without going searching around. If people are interested only on the various skin packs feel free to use them by themselves or with other battle mods. Naturally there are also other little modifications done by myself and more will come (as for example different sizes for African Elephants or Easter Horses).
- Legionaire all around skin
- Osgreek royal peltalts
- Maximus183 oriental units
- Laigle celtis galae
- Octiavian31 kaziel roman
- Arstudio carthaginian units
- Épaminondas "unique colors"
- Indian Armored Elephants scale mail and Royal Cataphracts gold armor textures by FarSovereign.
- Reworked units visual height and size.
- Revisited uniform colors of factions to render them more unique. A great thank to Athalwulfs on which mod I based this changes with some minor alterations.
- Reworked visuals on many units to represent the changes in the mod.