The Iron Tabernacle is close enough to some of the lower reaches and fissures in the Underdark that monsters from below occasionally find their way in and set up lairs in one shrine or another. The dwarves impress upon the characters to be on their guard, or to take guards with them, if they visit. From time to time, the sound of combat rings through the tabernacle hallways, a contrast to the chanting voices of the priests and a sure sign that something unwelcome has made its way into this most sacred of places.

(c) Chapter 8 "Audience in Gauntlgrym", Out of the Abyss, Wizards of the Coast