So recently my party and I were in combat with a large homebrew fiend. As a paladin I used the turn the faithless feature and the creature failed its saving throw. Our dm instead of taking the dash action decided to use the spell dimension door and ended the combat, but seemingly with an undertone like we screwed up by turning it. My question here is can a creature use a spell even if it is a bonus action even though the feature turn the faithless specifies that the only action it could take was a dash. What do you guys think? I been playing since 3.5 and never seen or heard of a creature casting spells when it is turned.

Well, the Turn the Faithless feature doesn't say that the tuned creature can't cast a spell. It does say that the target must use its turn to move as far away as possible from the paladin, that can use its action to Dash or to try to escape from an effect that prevents moving. So, if the target can cast Dimension Door as a bonus action and use it to flee, I think that is fair.

Thank you :)

It almost 1 shot our Barb  >.<