N. Ancient altar

An old, genuine altar of black marble veined with red, consecrated to the black spider goddess of the deep elves. The tabletop is broken, the pillars toppled. It gives off an ominous aura. A myriad of tiny red and black spiders swarm over the remains. A secret passage (to O) in one of the north tunnels opens when a fake stalagmite is pushed in, with a muffled squeak, and closes with a loud clack! sound.

• → Ominous aura. Within 6' radius: WIS check or disadvantage on all rolls for 4d10 minutes