In Ysgard your enemies will come back even if you kill them, so your only options are trapping them, killing them while they're not on Ysgard, or finding a way to make them not your enemies anymore.
Each of those has numerous ways they could be used in an adventure.
True, however, they are your enemies today, and perhaps allies tomorrow. Such is how I see the chaotic nature of that plane.
"Eskar, you dog! How come you back here?"
Crap... "Bevlin... I need to cross this pass to reach the the town of Hammerslay. Don't think to stand in my way, for I have in kin need!"
"Kin in trouble, eh?" Bevlin smirks as he puts his arm around his cousin's shoulders. "This one gets neck deep in hot water often enough. How much trouble?"
"Enough that I may need to gather a dozen strong fighters in town. He tried to steal some idol from a throng of scalies."
Bevlin looks over at his cousin, "Listen Ollin, this one took my head clean off with a clever swing of that axe yestereve. You watch yourself around him. And you," he points to Eskar, "don't think I'll fall for that trick again! Scaled folk, you say? That could be interesting... Plenty of glory or just a bash-about?"
Well, well... "I imagine there will be enough glory for a dozen of us, and plenty of jet and lapis that they hoard to pass around. Interested?"
"Let's go! We're bored sitting in this pass. Come on, Ollin!"