Spaceship Tet (InstanceTopic, 9)
From Compile Worlds
Teto, or possibly just Tet, is the name of a spaceship that appears in Puyo Puyo Tetris. Presumably, the characters T, S, I, O, L, J amd Z are minding their own business on board their ship when the Puyo characters magically and accidentally teleport there, scaring the crap out of them and making the two groups of characters naturally antagonistic towards each other. Though there is a set of seven thematically named characters aboard the ship, with several being related to one another, none of them appear to be a boss character, leaving the identity of the boss to be Satan unknown.
Etymology
The name as it appears in Japanese involves the kanji 号 (ごう gou), though there is no evidence to suggest that 号 means "spaceship". However, 号 can be used to refer to the name of a vehicle, and the thing being referred to is definitely a spaceship as seen in the Puyo Puyo Tetris stage select screen.