Thordak

Thordak, "the Cinder King", is an ancient red dragon, even larger than other ancient dragons. He is (presumably) the leader of the Chroma Conclave.

Background
Long ago, Thordak lorded over the desert continent of Marquet. Eventually, he attacked Ank'Harel, but he was gravely wounded and retreated until about fifteen years ago. He resurfaced, ruling the island of Viscaln in the Lucidian Ocean.

Before the events of Critical Role, Thordak destroyed Byroden, killing Vax'ildan and Vex'ahlia's mother. At some point, Lady Allura and her adventuring party sealed Thordak in the Elemental Plane of Fire, at the cost of three party members' lives.

During the Stream
In, Vox Machina saw Thordak while Keyleth progressed in her Aramente with the Fire Ashari. It is currently unknown how Thordak later escaped from the Elemental Plane of Fire after those events.

In, Thordak led the Chroma Conclave on an assault against Emon, Westruun, and (presumably) other parts of Tal'Dorei.

In, Lady Allura and Keyleth revealed through a scrying ritual that Thordak had returned to the Material Plane through Pyrah, completely "decimating" it in the process.