From The Heroes of Might and Magic III wiki

[edit] Warren

The Warren is the level 1 dwelling of the Dungeon town. It produces Troglodytes at a rate of 14 a week.

Requires: Fort

Cost: 400 Gold, 10 Wood

[edit] Upgraded Warren

The upgraded Warren allows the production of Infernal Troglodytes

Requires: Fort and Warren

Cost: 1000 Gold, 5 Wood