The Cauldron

"We were facing a full squad. I recognized a couple of them—Orsa, Teben—but they were different. Decked out in dark gear and set to intimidate. I took it as an attempt at psychological warfare— up the creep factor in a creepy place. But it was more than that. They had changed."

- Warlock describing an encounter with the Shadows of Yor

The Cauldron is a Crucible map located on the dark side of the Moon.

Grimoire description
"Every inch of this place feels wrong... tainted. Makes your Light itch. Just ignore it and keep firing."

- Arcite 99-40

ARENA DESIGNATION: The Cauldron LOCATION: The Dark Side, Moon

The Warlocks' most lucid theories assert this crumbled husk of a Hive ritual site is one of many ceremonial transmogrification chambers hewn beneath the Moon's crust.

Now secured and maintained by the Crucible, scheduled study of it's remnants suggest a sacrificial purpose—where other forms of life were given an audience with the reigning monarch and judged before the power of the Darkness.

Trivia

 * Back in The Dark Below expansion, it shows the bodies of various species when the Guardians spawn in, not only Humans and Fallen, but also Cabal, this would point that there were Cabal troops on the Moon and interacted with the Hive and Fallen at some point before their initial confrontation with Oryx's forces on Phobos, the House of Wolves on Mars or the Grasp of Nokris during the Red War.