From WoWWiki

Background

Orc Captives are nonelite mobs found inside The Blood Furnace. They have been captured from Thrall's Horde to be converted into Fel Orcs under the command of Kargath Bladefist. They are found twice in The Blood Furnace, The Maker's room and the beginning of the Broggok event.

Abilities and Info

• Shadow Word: Pain - Mild shadow Damage over time debuff.
• Heal: Heals for a medicore amount.

The Orc Captives in The Maker's room can be aggro'd even known when they are inside their cages (atleast in Heroic mode) but cannot be prematurely aggro'd from their cages in Broggok's room.

Notes

It should be noted unlike mostly every other mob in The Blood Furnace, Orc Captives DO NOT yield Thrallmar or Honor Hold reputation at death.