The Tumor

The Tumor is a mysterious object found at the center of a fully prototyped Skaia. According to Rose, the Tumor is likely a time bomb set to detonate when the Reckoning ends, in order to wipe out null sessions that have failed to accomplish the game's goal. She states however that this is mere speculation on her part, and that it might not be a common game feature and may indeed represent a mutation specific to the kids' session.

The Tumor seems to have a white and black half, similar to a Taijitu, the implications of this are currently unclear, although it seems to relate to the chess theme and the Prospit vs. Derse duality. It may also be a reference to both the Magic Cue Ball and the Magic Eight Ball since it features a round window in its middle that reveals a triangle displaying a countdown.

John was able to retrieve the Tumor after fully understanding of his powers as the Heir of Breath. Once John retrieved it, he sent the Wayward Vagabond the Courtyard Droll and Liv Tyler to deliver the Tumor to Rose, who was to wait on Derse for it. Rose planned to travel to the Green Sun to destroy it in the detonation, using a route she expected Dave to map out. She devised this plan with the help of The Noble Circle of Horrorterrors, who want to save themselves, and, who wants to die by destroying the Green Sun.

The Courtyard Droll attempted to steal the wallet which the Tumor was stored in, but Liv Tyler took the Tumor card. She delivered it to Rose and Dave on Derse. Rose and Liv Tyler left Derse by flying away on its moon with the Tumor.

The Tumor's relation to Karkat skipping the last genetic sequence to create the Troll's Bilious Slick, thus "giving it cancer," is unknown, if even existant.