We're All Fiends Here

From publisher blurb: 5th Edition Mini-Dungeon for four to six characters of levels 5-6 Over the last several years a group of fiends have been desecrating a once hallowed church. Their goal is to summon their master and gift her a corrupted relic stored behind sealed doors. The withered old church is nothing but a husk, the interior long since abandoned. The once well-polished floors have given in to years of rot and now reveal a set of stone stairs leading down.