Riveneye said:How am I meant to play a fiend though? I'm in a party of neutral and good people. I'm just having a little trouble picturing what a fiend would do in a situation like this (besides kill everyone and run around wild).
You can take the old dilemma to your character: you are good, but has been deceived by a fiend and so, your soul is lost, evil has tainted you and you must live with it... you want to be good, but sometimes evil speaks louder.
Just try your best to roleplay the internal conflict, and maybe sometime your DM will allow your group the chance to find this fiend and claim your soul back, releasing you from your destiny: to join the infernal forces against the light, maybe even participating in the blood war...