The Masochist would provide the essence, and Occisor the sustenance. That was the symbiotic exchange of the two Primal Demons.
Powers: The brutality of Occisor came with the wriggling worm, as the creature's touch could harm any that came into contact with it, the larger the area and the lenghtier the time of contact, the more damaging it was. This made Occisor near-untouchable, leaving the Sunguard to attempt to keep the Demon at bay with ranged assaults. The creature also possessed a collar of branch-like protrusions, that at will would also grab hold of any that came near the back of the worm, draggin the victim to its forest of edges. Also, Occisor used the Masochist's provided essence, it's blood, as a means of movement and lubrication, for it was that essence that the Murderer used to create a slippery surface on the hollowed-out portion of it's body, to move around, wriggling and twisting on the ground, and while the surface of this blood-like essence was solid, underneath the solidified membrane the liquid fueled the dry body of the Demon, allowing it to twist and curve it's body in any way it desired.
Defeat and Aftermath: With the Traitor attacking the Masochist and leaving it weakened, it could not share any of it's blood-like essence with Occisor, and soon, the worm creature began to slow down, it's movements clunky, until it dried completely, while attempting to flee it's demise. The Sunguard removed it's skull from the rest of the body, to keep the Demon's presence away from it's body, and where the worm's body crumbled, it formed a hollowed path, that would eventually become the river of molten blood, eons after. The branches would find minimum comfort on the remnants of the Masochist nearby, surrounding part of Occisor's open corpse, contaminating and preparing to form a full forest, though weak and broken, aging quickly and snapping with the greatest ease. As for Occisor's skull, it was hidden at the edge of a cliff, far from the rest of it's body, to be buried by dust, ashes and sand that would pile over it.