Karrthus, Tyrant of Jund
Legendary Creature — Dragon
Flying, haste
When Karrthus enters, gain control of all Dragons, then untap all Dragons.
Other Dragon creatures you control have haste.
Dave Kendall
Double Masters (2XM)
• #205Rulings
When the triggered ability resolves, you'll untap all Dragons, including the ones you already control.
(wotc • 2020-08-07)
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.
(wotc • 2020-08-07)
Rulings
When the triggered ability resolves, you'll untap all Dragons, including the ones you already control.
(wotc • 2020-08-07)
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.
(wotc • 2020-08-07)