Kittum

WARNING: DETAILED PLOT SPOILERS AHEAD

Kittum is a denizen of the now-ruined world. They used to be a whole person, but due to ambrosia usage split into two separate bodies. Their minds are still connected, though, and is one consciousness controlling both bodies simultaneously. Despite this, the two have subtle differences in behavior, with the orange one being more outgoing and the purple one being quieter and somewhat shy. The reason for their unique predicament is the result of Yggdrasil's efforts to keep them combined, which did not work and resulted in Yggdrasil's current state.

They devised the "game" of using pawns to try and reach the city above to stall for time while they and Patience investigate a method of reversing ambrosia poisoning, mostly for Yggdrasil's sake. Using a device they helped develop called the Mirror Tower, they ripped five of the six characters out of their worlds and timelines to participate.

Before The End, Kittum was a high ranking member of a clique of researchers into multiple areas of science, who began studying ambrosia intently after its sudden appearance.

They belong to a cult who worships The Waking Dream, where unknown primordial entities reside - at one point she researched how to access and harness this realm of infinite energy. However, what she saw was eldritch and horrifying, leading her to abandon her research into harnessing it. The Mirror Tower is built on the technique of "pinging" into the Waking Dream and receiving information back from across it. Members of the cult are usually dressed in harlequin based outfits, with masks and patterns called Motifs on their clothes. Kittum's motif is checkerboard patterns, which Elias inherits.

Medimsha is her brother, and he worked with her before The End. They lost contact shortly after the collapse, with Kittum choosing to descend to the surface while Medimsha remained in the city ruins far above.

While they used the Mirror Tower to import the other participants, Kittum actually created Elias from research into creation of homunculi. He has no knowledge of this until late in the story, and it causes him an immense amount of distress.