#tear

Here the reference of Insanity Tear

So…

INSANITY TEAR’s story takes place in Underfell.

The original Tear was dragged into experiments conducted by Fell Alphys, which caused him to go insane and mentally unstable—very similar to Insanity Sans’s condition.

Because of those experiments, his body mutated, which is why the position of his mouth changed.

He is extremely obsessed with blood. He will kill any human or monster he saw to drinks their blood. The blood is stored inside the cotton within his body, so the blood leaking from his head and staining his clothes is not his own.

His original attacks, which used to involve tears, were replaced by blood. The blood overflowing from his eye sockets is the blood he has stored.

Ok, thats all

Tear Sans by @eriscary

"No radiant pearl, which crested Fortune wears, no gem that twinkling hangs from Beauty's wars. Not the bright stars which Night's blue arch adorn, nor rising suns that gild the vernal morn, shine with such lustre as the tear that flows down Virtue's manly cheek for others' woes" (Erasmus Darwin). 

Source details and larger version.