Unseen Ally: Killer.
Killer - A unit with Killer can make one special attack directly against an enemy unit. This can be done the turn it's played, and can target any unit, regardless of Flying, Aegis, or other special abilities.
Overwhelm - A unit or spell with Overwhelm will deal any excess damage to your opponent on your turn (does not work while blocking).
Ally - Happens as soon as you have a unit of the named type. This can be when you play the unit with Ally or later if there's none of the needed type in play. Ally resets if the unit dies or is returned to hand.