Acheron

is traditionally one of the Planes of Existence beyond the Divine Gate, embodying lawful/lawful evil. It has not yet been mentioned in Critical Role.

Characteristics
Acheron is said to be an infinite battlefield, embodying the ideal of order in battle. It represents the more lawful aspect of lawful evil.

Inhabitants
Acheron is the native plane of multiple evil deities including Bane, god of Tyranny, and Gruumsh, an orc deity. Laduguer, the duergar dwarven idol is said to reside here as well.