Deathdusk Passage

From the Introduction:

Deathdusk Passage is a collection of three short encounters designed for five players of 1st to 3rd level, taking place in an ominous underground tunnel that connects any two locations of your campaign.

After entering the tunnel, the adventurers will become trapped in a hallway where they must fight off oozes and attempt to escape. Next, they will discover a dangerously deep pit; while attempting to cross, monstrous bats will descend upon them and attack. Finally, as they near the exit, statues surrounding an ancient gate come to life, attacking the players as they try to make their escape.