Umbral Mantle | Magic: The Gathering
Formats Umbral Mantle is Legal in
Official Oracle Text for Umbral Mantle
Official Rulings for Umbral Mantle
5/1/2008 : 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.
5/1/2008 : 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.)