MTG Keyword Rules — Comprehensive Rules Glossary

Power-up is a keyword that adds additional rules to the activated ability that follows it. “Power-up — [Cost]: [Effect]” means “[Cost]: [Effect]. If this permanent entered this turn, this ability’s cost is reduced by this permanent’s mana cost. Activate this ability only once.”

Generic mana in the permanent’s mana cost reduces generic mana in the cost to activate its power-up ability. Colored and colorless mana in the permanent’s mana cost reduces mana of the same type, and any excess reduces that much generic mana. (See rule 118.7.)