Tartarus is another name for Carceri (used in 1st edition AD&D). It is the prison of the elder titans and other primal beings.
In 2nd edition Legends & Lore, Tartarus was identified as a sibling of Gaea, Eros, and Nyx.
Oh...... Damn. But it was so hard, I felt like I was there.
— A Sensate after being told they hadn't been touching a sensory stone
