Why they abandoned it?

Ten reasons why the building / fortification / village / town was left by its inhabitants. Prepare your dice.

1. They were killed by a plague (there's 25% chance that they became the undead and are still around)
2. Ancient curse has fallen on the area. They left to avoid its effects.
3. All inhabitants were killed by 1-2: goblins, 3-4: bandits, 5: undead, 6: mutants.
4. They left to avoid the war.
5. They were captured by a slavers.
6. They joined the pilgrimage of followers of the Cthonic Gods.
7. All inhabitants went insane and commited suicide.
8. They left because famine plagued the land.
9. All inhabitants were transformed into 1-2: ordinary undead, 3-4: werewolves or other zoanthropes, 5: mutated, hideous monsters, 6: vampires.
10. They temporarily relocated to their hunting grounds / winter court / fortified stronghold.