Hateflayer
Eventide — Rare
Creature — Elemental
Hateflayer rulings:
2008-08-01: If the permanent is already untapped, you can’t activate its ability. That’s because you can’t pay the “Untap this permanent” cost.
2008-08-01: The “summoning sickness” rule applies to . If a creature with an ability hasn’t been under your control since your most recent turn began, you can’t activate that ability. Ignore this rule if the creature also has haste.
2008-08-01: When you activate an ability, you untap the creature with that ability as a cost. The untap can’t be responded to. (The actual ability can be responded to, of course.)
2008-08-01: Wither applies to any damage Hateflayer deals to a creature, which includes both its combat damage and damage from its activated ability.