You can call up to 5 Alter Egos after obtaining Rhapsody in Crimson. (Note: If one has summoned 5 Alter Egos, and summons the Adventuring Fellow next, all Alter Egos get dismissed. One must always make sure that there's a slot for the Fellow before summoning it).
You can only summon one copy of each Alter Ego. This includes when one character has multiple versions (e.g. summoning Zeid II prevents summoning Zeid).
These Alter Egos support you in battle with the strategies and tactics you've come to expect from them.
Alter Egos do not act except in battle, which officially starts after engaging and meleeing once. They will stop acting when you disengage.
If you kill a monster and auto-target another that has aggroed, some Alter Egos will cast spells on it, but they will not melee until you melee.
Trust magic can only be cast when not already involved in battle.
Certain instanced content will allow summoning even after initial aggro, but not after the player or another player in the party takes direct action on the monster.
Alter Egos use a wide variety of weapon skills, and will frequently attempt weapon Skill Chains, and corresponding Magic Bursts. They gain weapon skills at much lower levels than players would. Just like in regular parties, careful consideration of what weapon skills an Alter Ego can use will result in better performance overall. Try pairing your Alter Egos with other Alter Egos with which they can perform these high impact moves.
Because information on who can chain with whom is not well documented, players are advised to do their own research and experimentation.
Some Alter Egos have synergy with other Alter Egos, such as Trust: Uka Totlihn and Trust: Mumor (waltz potency). You can narrow down who possibly synergizes in some way with whom if they talk to each other when summoned.
Alter Egos' levels and attributes vary based upon the summoning player’s level and/or Item Level.
For regular levels, Alter Egos don't automatically level with the player. They must be dismissed and resummoned to match the player's level. Item Level changes are reflected immediately, which can be problematic with gear swapping.
Alter Egos are not affected by zone potions obtained in blue caskets.
Trust Magic does not cause magic aggro.
Trust Magic cannot be cast while silenced.
Alter Egos are dismissed if the player is Charmed.
Alter Egos no longer despawn when spawning Voidwatch NM, making them usable during these battles.
Initiation quests for the Trust initiative are available, and you learn the first spell as you progress. Additional Alter Egos can be unlocked through completing various missions and quests.
Some Alter Egos, however, can only be obtained by trading specific items to an NPC offering the initiation quest. New Trust spells will continuously be added in future version updates, though SE has stated that they are nearing the limit of new additions.
Trust magic is not available in all areas or types of battle content, but may be expanded in the future.
Special Alter Egos act very differently compared to players. They may also have a regular job as well.
Monster Alter Egos are non-humanoids that use their species' special moves. They may also have a regular job as well.
Passive Alter Egos are non-interactive NPCs that give a bonus as an aura. Most are technically Geomancers, but do not have to cast or recast. They cannot be interacted with in any way and will do nothing else but follow the leader.
Some Alter Egos have Auto Refresh, but no other indication of what subjob they possess.
Some Alter Egos have forced attribute bonuses that may make them more or less useful for certain situations. For example, Selh'teus appears to have a capped hit-rate regardless of content level, and Lillisette II has a very high crit-rate (75% on Apex Crabs) independent of content level.
Usage in Parties
Players can summon Alter Egos while in a party containing other players.
Only the party leader is able to summon forth Alter Egos.
Alliancescannot be formed when in a party comprised of both players and Alter Egos.
After joining a Unity Concord and getting a Partial Personal Evaluation of at least 5 points, you gain access to your Unity leader immediately. You lose access to your Unity leader if your Unity Personal Evaluation drops below 5 at the weekly Sunday conquest points tally, but you regain access as soon as your Partial Personal Evaluation reaches 5 again. You do not have to wait for the next weekly tally.
To see Unity info, from the right-hand menu, choose Status > Unity.