|Blast from the past!|
Enemy Ability: Terror
Greatly delays target hero.
Self Ability: Shriek
Deals armor-piercing damage and delays the whole party.
While Zeitgeists aren't really dangerous on their own, their delaying can really break your party's strategy, and they should be taken out as fast as possible.
Abilities that produce passive buffs are great idea when fighting Zeitgeists, as they allow the hero to remain useful to the party even if they can't move. The best examples are Blind Archer's Ear Shot, Pyra's Cauterize, or Knight's Protect.