Murkk is the creature that was formed from Dusq's joining with Nightmare Meen. He was initially destroyed by Invader A, causing the Nightmare Dimension to crumble. However, he managed to reform, and has become Invader A's main nemesis.
As Murkk is basically a fusion of Dusq and Nightmare Meen, he is basically a black and gray version of Nightmare Meen with glowing orange eyes.
His PAK is replaced by a shadowy mass.