Slaves of Núrn are farming NPCs found in various structures in Near Harad (Biome). They spend their days tending farms or standing sadly in cages. They are easily recognizable by the hoe they hold in one hand. Although they are technically part of the Near Harad faction, good NPC's won't attack them.
After having bought one, your submissive "possession" follows you around (also through fast-travelling), calling you "Master" until you decide to interact with it by right-clicking. You can talk to it and you can also dismiss it. So, the best use for it, is to seek a suitable place to start a new farm. Rabbits will also not try to eat crops guarded by slaves.
They work similarly to other farmhands. They will help you sow and harvest crops if you give them the seeds. For more information, please check the farmhands page.