From The Heroes of Might and Magic III wiki

[edit] Wolf Pen

The Wolf Pen is the level two dwelling of the Stronghold town. It produces Wolf Riders at a rate of 9 a week.

Requires: Fort, Goblin Barracks

Cost: 1000 Gold, 10 Wood and 5 Ore

[edit] Upgraded Wolf Pen

The upgraded Wolf Pen allows the production of Wolf Raiders

Requires: Fort, Goblin Barracks, Upg. Goblin Barracks and Wolf Pen

Cost: 1000 Gold, 5 Wood and 5 Ore