The creature is alternatively named "Jack" and "The Thing with the Legs in the Path to the place where the Thing with the Quivering Jaw is"
Overview
Vomiting Diglett is a huge monochromatic monster that can be found in the path between White Desert B and the place of The Thing with the Quivering Jaw.
Its right eye looks like being thorn out and vomit some white juice across the path. It has two legs and its bottom looks like sticking on the ground or grows on the ground.
Pressing the up key from the path will make the screen roles up to see the full appearance of it.
Speculations
It is possible that it represent a Man's Ejaculating Penis due to its appearance, as for Madotsuki enters the entrance that looks like a man head, it could be meant of what Madotsuki thinking about men's minds when looking at her which is link with sex, and come out from a nose bleeding Buddha which be considering as Kenja Time (賢者タイム, Sage Time, mean after ejaculation), causing Madotsuki meets her deepest memory of anger as the Thing with the Quivering Jaw.