text: Training Grounds can reduce the amount you pay for a creature's activated ability cost that includes {X}. For example, Drana, Kalastria Bloodchief has an activated ability that costs {X}{B}{B}. If you control Training Grounds and you activate the ability with X equal to 5, you'll have to pay only {3}{B}{B}. This is true even if the ability states that {X} must be paid with a certain color of mana, as Crimson Hellkite's ability does.