The other comments really say what is needed here. Right now they feel like cardboard cutout villains to fill the 'burn the witch'. There is good drama potential with how they deal with heretic priests and the like. Go to Comment
This is quite a good item. Moons comments about the effects on the character is a good one - being in literal Hell should leave a mark.
I would at least have the user now have infernal _attention_. It is not often that a soul gets to leave that place. I'm reminded of an old Dragon magazine comic that showed a character who managed to escape hell one time being waited for by a 'welcoming' committee after his final passing..