
TrampleTrampleExcess combat damage it deals to a blocker carries over to the player or planeswalker it's attacking.
When Bumi enters, earthbendearthbendTarget land you control becomes a 0/0 creature with haste that's still a land. Put two +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped. 4.
Whenever Bumi deals combat damage to a player, untap all lands you control. After this phase, there is an additional combat phase. Only land creatures can attack during that combat phase.
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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.