The real Ruby Ring is obtained from the Jempek Governess and provides mana regeneration. This quest has two possible outcomes, so take care when choosing whom to give the slave to.
Quest steps
Ask the Jempek Governor about help. He will ask you to fetch a particular slave from the Jempekian slave tent.
Go to the Jempekian slave tent and purchase the correct slave requested by the Governor.
Instead of returning the slave to the Governor, take the slave to the Jempek Governess. She is secretly trying to free the slaves and prevent her husband from exploiting them.
Give the slave to the Governess to receive the real Ruby Ring with its mana-regeneration magic.