>>28961022She really looks like a ghost slug(their love horn is even redish to boot), those have a love horn they trust into another slug to make it act as the female, then they mate.
It makes sense they are in the same egg group as other slug given that ghost slugs where thought to be a fairy that protected houses against the plague, in reality the slugs habits helped to ward off the mice and other garden pests in the country side.
