Some demonic creature doodles. These first few are ideas for infernal dignitaries, ambassadors, their bodyguards and translators, etc. The hammerhead shark guy in the top right is of course inspired by the Dayak from Enki Bilal's Immortel.
Naturally, the boss of Hell would have to be the Krampus, Prince of Punishment.
A few more. Classic demons would actually be invisible and bodiless, so as you can see, I included a few of these as well.
Finally, some giant robots. I guess I just have a fondness for oversized heads.