xyz question

how do instant fusion and mist archfiend interact as xyz material, do they get deattached at the end of the turn and in the case of mist archfiend do you take damage?

i dont know about mist archfiend but im 99% sure that if you xyz with an instant fusion monster your good to go and dont lose the monster at the end of the turn

When a monster become Xyz material, it isn't a monster anymore. Any effect that would comes from the monster will not activate, apply or anything. So Mist Archfiend won't get detach and the same for Instant Fusion.