So its a natural part of their lives, as inevitable as death, for those who choose to use magic right?
or does it burn passively? if it only burns when magic is used, most people would rather not use magic [I'm assuming living in the volcano is possible without actively using magic because of...
No such thing as a boring magic system, only boring authors, and stories. The most successful books actually have pretty plain almost boring consequences for magic,
How you incorporate the consequence into the story is what would keep readers immersed.
But this idea in particular is not boring...
You can use an imp. It's not necessarily evil but They are notorious tricksters and attention seekers. If you're wondering how it looks imagine A demonic fairy with bat wings.
And the good part is it doesn't have any specific magic powers so you can give it whatever you want.