Khloros

During the Fall, Genubath stole one of the prototype horses from the Hall of Creation. Unsure what to do with the beast, the Prince of Rapine gifted it to Beelzebub, who in turn used its Forces to craft a djinni steed for the young Thanatos, then a courier between Corruption and the War.
When the Fourth Seal is broken, Khloros will abandon Thanatos for a time; attuning itself to the Pale Horseman instead.