Naka

''Coffee didn’t grow well on the Eden Road, and was prohibitively expensive to either grow or import. The discerning Milky Way Cultist’s alternative, naka, was a highly-caffeinated lichen hybrid that boiled up into something that tasted like socks but at least kept you awake just in case someone poured more of it into your mouth when you dozed off.'' - Greyblade

A preferred beverage of humans living on the Four Realms staircase, naka is an ancient artificial lichen hybrid optimised for growth in cold temperatures and thin air.