Killing enemy units grants experience to nearby Royal Guards. If there are no nearby Royal Guards when an enemy is killed, the experience is instead split between all Royal Guards in the mission. Experience allows the unit to gain Rank, which improves its damage, armor, health and unlock new abilities or passive bonuses.
Rank 1: Deals bonus damage to Massive targets.
Rank 2: Gain the Tactical Realignment ability.
Rank 3: Gain the Evasive Maneuvers and Phoenix Protocol abilities.
The leveling up mechanics works as follows:
When an enemy unit is killed, 100 experience per supply cost of unit killed is "dropped".
If the unit is a non-Heroic unit with 0 supply cost, it will drop no experience.
If the unit is a Heroic unit with 0 supply cost, it will drop 800 experience.
Dropped experience is equally split among all eligible units (Royal Guard, not at max rank) within 15 range of the unit killed.
If there are no eligible units within 15 range of the unit killed, all eligible units on the map get an equal split of the dropped experience.
Once a Royal Guard unit has reached maximum rank, it is removed from the pool of eligible units so as to not waste experience.
Mastery: Increases the gained experience per supply by +0.5 (+4 on Heroic unit with 0 supply cost) per Royal Guard Experience Gain Rate mastery point. Up to a maximum 115 experience per supply (920 experience on Heroic unit with 0 supply cost).