mephistopheles (project moon)

A bus with a Steam Locomotive-like exterior that serves as the Sinners' mode of transport and living quarters.
Its engine was developed by Faust, and its mirror technology (which allows access to the many ingame alternate identities) was partially developed by Yi Sang.

It is operated by Charon, who calls it Mephi.

In literature, Mephistopheles is the demon that offers the doctor Faust vast knowledge in exchange for his soul.