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Flying, haste
When Karrthus, Tyrant of Jund enters the battlefield, gain control of all Dragons, then untap all Dragons.
Other Dragon creatures you control have haste.
The control-change effect of Karrthus's triggered ability lasts indefinitely. It doesn't wear off during the cleanup step, and it doesn't expire if Karrthus leaves the battlefield. In a multiplayer game, it does expire if you leave the game.
When the triggered ability resolves, you'll untap all Dragons, including the ones you already control.
