no problem :) Can you accept my answer as correct for future viewers.

Just checked my copy and yes the villain (a dwarf called Zinixo) was trapped in a magic bubble by Rap - "I wrapped him up in an unbreakable soap bubble that stopped magic. He still had his power then, but he couldn't use it."

It is a while since I read them so I am not really sure. Having said that there are definitely dwarves in the story and being trapped in a magic bubble sounds familiar