Molten Weeper is an altered created by an entity believed to be Slenderman , although that has yet to be confirmed. It appears a being made of lava, although it seems to be located internally rather than being 100% out of lava. It's eyes on its head seem melted, although the eye on its stomach seems like it was embedded there.
It is neither for nor against Slenderman in particular, but is hostile towards anything that hurts The Weeping Willow . It has some kind of affection for it and will not tolerate any hostility towards her. It tends to be neutral to helpful around regular humans and actually likes interacting with them, at least the ones that don't run away.