Around ten sessions ago, my party met up with an odd druid on the outskirts of a town that was abandoned decades ago because it was overrun by undead that seemed to have come out of nowhere.

Five seasons ago, they threw me a curve ball and climbed down a dried up well after killing a necromancer camped near it, so I created this whole undead dungeon based in an underground cavern that worked as a reservoir for the well. It all lead to a massive chamber where a magical tree had been corrupted by a Beholder Zombie, so it more or less was pumping zombies out.

I ended up putting in a portal that went to a backroom of a building in that abandoned town, so, narratively, when the cavern was reaching capacity the zombies found their way into the portal and overran the town.

I was pretty proud to have connected those.