The Keeper appears as a human child with raven-black hair and dark eyes. He lives in a space between worlds, which consists of gray marble hallways with a mulititude of doors. He rescued Cordan and his friends both times when they escaped from Other Mother.
The first time the Keeper rescued Cordan, he warned him of the danger Cordan would be in if he returned to Sigil with the bladed dagger. Cordan chose to leave the dagger with the Keeper. However, when Cordan became trapped in the watery demiplane, Other Mother escaped her prison and killed the Keeper and stole the dagger.
Although he had died, the timeless nature of the hallways prevented the Keeper from truely dying. He later aided Cordan in defeating Other Mother, and then resuced him and his friends from the collapsing realm.