Mechastopheles is a series by Gordon Rennie, Lawrence Rennie and Karl Richardson which runs in 2000 AD. It first appeared as part of the Tharg's 3rillers series in prog 2045 (2017), before returning as a series in its own right in prog 2092 (2018).
The story takes place in a world where the Biblical Apocalypse has taken place, and Earth is overrun with demons. The last few surviving humans have taken refuge inside a colossal robot animated by the soul of a demon bound to it, serving both as a shelter and as humanity's only line of defense against the forces of Hell.
In other words, it's like Neon Genesis Evangelion on even more drugs.