Hagfish are blind, though the simple eye that they possess actually is a valuable tool in tracing the evolution of more complex eyes. To make up for their blindness, they have exceptional senses of touch and small. Hagfish are able to search out meals on the dark sea floor using said senses, and these meal often consist of small sea-floor worms. However, Hagfish have a secondary, quite gruesome feeding method. They can attach themselves to dead or injured creatures that are much larger than themselves. They are then able to burrow in to the body of said animal and literally consume it from the inside out.
Another gross thing about Hagfish? The slime. Hagfish secrete a thick mucus from their bodies that serves a a defense mechanism. It is said that a single adult hagfish can secrete up to a gallon of this mucus at a time. The mucus is also full of tiny fibers that make it exceptionally thick and difficult to deal with.