what about a sad twist on the usual selkie story, where during the Kraken Era, the Trauma Crew assume Ed has Izzy's coat, and that's why Izzy can't leave even though he's bearing the brunt of Ed's abuse. They even go searching for it, to help him!
But then Jim finds Izzy's coat, ragged and neglected, stuffed in the back of Izzy's closet. Ed threw it in his face in the regretful, bloody aftermath of a Punishment Session and told him to leave unless he wanted Ed to kill him. But Izzy didn't. And Frenchie, Jim, Fang and Archie realise that what binds him to Ed is far harder to dispell than magic.
I just want everyone assuming there's an easy fix to getting Izzy The Fuck Away to somewhere safe, only no, it turns out Izzy is deep in the mentality of 'I deserve this' and 'I can't leave him' and 'he needs me' and 'he loves me really, deep down'.