Umber Hulk (Large aberration)

About 8 feet tall, stocky and covered with chitinous natural armour, these massively muscled insectoid horrors somewhat resemble a cross between a gorilla and a gigantic beetle. They tunnel through solid rock as if it were light undergrowth. Their huge mandibles and clawed forelimbs can tear and crush most armour with ease. With a pair of compound eyes and another pair of simple eyes between them, they probably has some kind of enhanced visual senses. Meeting their gaze can confuse opponents.

In addition, the one the party has met so far seemed extraplanar in origin.