Collectible Card Game Headquarters

Describe the Bug:
When Mudslide's controller's opponent chooses to untap a creature without flying, Mudslide's controller is prompted to pay . That action can be canceled by the player (AI will always pay if it can.)

Thus, Mudslides's controller's opponent cannot choose to untap any creatures without flying when Mudslides controller does not have at least 2 mana available in mana sources or in their mana pool.

Which card did behave improperly ?
Mudslide

Which update are you using?(date,name)Which type(Duel,Gauntlet,Sealed Deck)
BfZv2, Duel

What exactly should be the correct behavior/interaction ?
When Mudslide's controller's opponent chooses to untap a creature without flying, that player is prompted to pay [2].

Are any other cards possibly affected by this bug ?
-

Confirmed for both players only Mudslide 's controller is prompt to pay in both players turns.

(Minimally) fixed in 22361f4.

Similar cards worth double-checking: Magnetic Mountain, Thelon's Curse, Dream Tides. In particular, if any of them work right (select all creatures, then pay all at once), then it should be factored out for all the others to use. I have no doubt that they're all just subtlely-differently-wrong cut-and-pastes of each other, though.

Thelon's Curse works, Magnetic Mountain is bugged, Dream Tides works. None pay all at once.

Magnetic Mountain fixed even more minimally in ccb1fb0.