The Japanese freeware game Yume Nikki has always been a wild inspiration to me, so I looked up this character sheet from the fanmade wiki for ideas. Number 35 on this list, the Henkei Shita, really called out to me. Other candidates were the Pirori (number 21), and the first train passenger (number 56).
Here's an isolated image:

The henkei shita (meaning 'deformed') is generally perceived to be a headless, pregnant female. Due to the horrific and violent imagery there, fans (myself included) feel this symbolises a fear of pregnancy within the female protagonist. People believe this could conclude she is terrifed of her own sex and wishes to change it, but the process and the male sex or gender terrify her, so this puts her in such immense emotional turmoil she doesn't know what to do. That's more or less my interpretation of the game.
They are found on a path connecting the Eyeball World to Hell. In Hell, a red version which bleeds yellow, with yellowed teeth and a yellow eye can be found.
In a way, this monster feels personal to me, too.



Unfortunately, this hasn't been painted yet. As of typing this, it's not fully dry, so I can't do much with it. When I do paint it, it will either be the first or last design in that above screenshot.