Lust Ring

The Lust Ring is one of the seven rings of Hell. It is not accessible to Sinners as they're confined solely to the Pride Ring. Hellborns, such as Imps, can be seen in this ring.

Trivia

 * The realm is likely alluding to the Nine Circles that was briefly mentioned in the series' pilot, which itself originates from Dante Alighieri's Inferno. Lust in particular is said to be the second circle, and is reserved for the licentious condemned.
 * It is safe to assume that he sky of the lust ring is pink, because greed (Greed Ring), which is often associated with green, has a green sky (same goes for Pride Ring) and Lust is often associated with pink as well, hence the sky being assumed to be pink.