Of course they'd have to tune it to be equivalent to early game weapons. But the option to have a completely new play style for a play through is very appealing.

I don't really see a reason to keep it completely restricted to the end game.

Variety is always great in games like this. Early magic weapons can just be lower damage/much more basic spells/effects. Then progressing to the mistlands unlocks the cooler spells.

I think I saw a Necromancer pet style spell? The early game weapon could start off with a small, relatively weak skeleton and progress into a larger skele warrior (or whatever the current version is).