If Ashes in Hades 2 are the equivalent of Darkness in the first Hades game Psyche is somehow also the equivalent of Darkness as well. To elaborate, in the first Hades game, you would spend Darkness to invest (and activate) different passive and active buffs to Zagreus. This could be effects like giving him extra charges of Death Defiance to getting multiple Dashes, as long as you had the Darkness you could activate it.