Base of the Rats in the Stormreach undercity. Entry is trapped — favored traps include tripwires, animals, and false ropes/bridges.
Entrance: a sewer near the Harbor — at the T intersection go right, then first left. Marked in thieves cant as “the sewer entrance to hideout 4”. Guards observed at the base of a ladder past the T.
Interior is ramshackle and patched together, not an organized system. Password by the ladder is written as “Exuurz vdih” (Caesar shift back 3 → “Burrow Safe”).