I just had a great campaign idea. A BBEG sets up a bunch of small dungeons with “keys” that when put together will access his main base for the party to break into.
The twist is these “keys” have clues that just lead to other “keys” and dungeons. The BBEG doesn’t have a lair but is trying to rid the empire/continent of their best heroes so it’s easier to take over.
There can be clues for the party like groups of dead adventurers in the dungeon or an easy one like a “key” just leads back to the start of the dungeon loop again.
I got this idea after seeing a lemmy post about ant death circles.
Map out the dungeons. On the map they form three arrows pointing to a place in the middle of the most dangerous desolate Level 23 dragon infested place. But if you make it a circle instead at the center is the BBEG’s place which is actually this wood carver hut in the woods NEAR the imperial city and it turns out he’s been making realistic looking wood golems the whole time and replacing key figures in the kingdom because they are loyal to him, the plot to get rid of heroes is just insurance.