
TrampleTrampleExcess combat damage it deals to a blocker carries over to the player or planeswalker it's attacking.
Agent Frank Horrigan has indestructible as long as it attacked this turn.
Whenever Agent Frank Horrigan enters or attacks, proliferateproliferateTo proliferate, choose any number of permanents and/or players, then give each another counter of each kind already there. twice. (To proliferate, choose any number of permanents and/or players, then give each another counter of each kind already there.)
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Read from the rules text. A card that enables a keyword makes or is the thing; a card that rewards it gets better when you have it. Two cards interact when one enables what the other rewards.