Larian Studios Forums Baldur's Gate III Baldur's Gate III - General Patch 8 introduced the first time I've ever been tempted to use the tadpole.

You're saying that Sorceress as a class in particular cannot use the rune to save Shadowheart?

Sounds like a bug rather than an intended feature to me. The whole point of the key, the chest and the rune is to provide the player with a guaranteed option to save her incase they fail all the other checks, such as the Barbarian pod smash.