So, I've been thinking, what if you pick up a random quest in Daggerfall and you have to travel to a dungeon which is in the Main Quest as well? Is that possible? I've heard that it can occur with Castle Necromoghan, I think I even encountered it once. But can it occur with Scourg Barrow, one of the Castle dungeons(I mean Daggerfall, Wayrest, etc.) or even Aetherius?
Or what if you pick up a "Kill a rogue imp" quest from the Mages Guild? They normally send you to Palace of RandomTown but can you be sent to Castle Daggerfall, for instance?

I remember there is a quest to kill a lich inside Scourg Barrow. There's a lever on a rock that rolls back a rock door. I think with the kill an imp quest that it's only the smaller castles without a guard staff that need an exterminator.

I meant those quests that you can do several times. Like a faction quest or an innkeeper quest. For example finding a book, and they send you to a Main Quest dungeon.
So with the imp quest it's always the smaller, but still important enough towns to have walls? I should have guessed. Thanks for the reply.

For miscellaneous quests, I've been sent to MQ dungeons a few times. I can't remember which ones, though.

Main quest dungeons are used as quest locations but:
you won't be sent out of the region in which you accepted the quest except for the rebel mage (Balthus Greyman?) quest from the Mages Guild which leads you to Direnni Tower, and the Lord K'avar quest from the Fighters Guild. There might be more quests this happens in, but these are the only ones I remember.