Why does the Enduring Angel from Innistrad: Midnight Hunt has the following text:
Then if Enduring Angel didn't transform this way, you lose the game
When does it apply?
Board & Card Games Stack Exchange is a question and answer site for people who like playing board games, designing board games or modifying the rules of existing board games. It only takes a minute to sign up.Sign up to join this community
Clones (like Clone) and tokens copies (created by effects like Cackling Counterpart) don't have a backside and can't transform for that reason. If you would have a copy or clone of Enduring Angel and it would transform you'd lose the game.
Also, if it would be under the effect of a card which stops it from transforming (like Bound by Moonsilver) you would also lose the game.
701.28c: If a spell or ability instructs a player to transform a permanent that isn’t represented by a transforming double-faced card, nothing happens.
I'm sure there are others, but probably the most common situation is if you make a token copy of Enduring Angel; because the token doesn't have a back side, it can't transform.
Perhaps the most well-known case here is Garruk Relentless - if you copied Garruk and then reduced his loyalty, the game would draw due to an infinite sequence of Garruk's "transform" trigger going on the stack, failing to do anything and then triggering again.