Some notes:
-You can only summon one spirit per target, but (currently) you CAN attack the target of your spirit
-Order of spirits summoned (and a form you take personally) seems to be random
-Your spirits retain your race and some gear
-Spirits always autoattack their target even if you don't, and they have Tiger Strikes just like you
-They can mirror your SCK and their SCK hits all targets nearby
Updates:
-Tried to duel a player, you can target a player but it won't let you attack it
-SCK is the only AOE tested, but that didn't do any damage
-Spirit was damaged by something once, probably Swift Reflexes
-Currently there's a bug that spirits won't keep you in combat, which lets you mount up and spirits will try to chase you instead of attacking their target, if you dismount they'll stand still and do nothing until dispelled