Item from Hades by Supergiant Games
The keys of the Underworld — used to unlock the Mirror of Night's deeper talents and open the Arsenal Room's additional Infernal Arms.
Chthonic Keys unlock things. The Mirror's deeper talents cost them. The Infernal Arms cost them. Resetting the Mirror costs one. They are the gating mechanism of the entire meta-progression system — you cannot fully explore either the Mirror or the Arsenal without accumulating them over many runs. They appear as room rewards throughout the Underworld. They can be traded at the Wretched Broker. They are rarer than Darkness but more structurally important — a key doesn't make you stronger directly, but it opens every door that does.
An ancient-looking key with a distinctly Underworld aesthetic. It has been redesigned at least twice in the game's development history, going from 'Skeleton Key' to its current form.
Also known as: Skeleton Key, Chthonic Key