Essentially, a fourty-foot rattlesnake with horns that can raise itself like a cobra. But unlike a rattlesnake or cobra it's venomless - because of its size, and thus the size of the food it needs, it couldn't pump enough venom into a victim fast enough to effectively kill it. Instead, it ambushes a victim, holds on with its fangs, curls around it, and impales it with the dagger its rattle evolved into. The horns are used to club the victim's head into a daze, and offer some eye protection against thrashing victims. Malrocs are actually fairly placid, and only attack if they're hungry or annoyed (and malrocs don't annoy easily).

I know, not a very original design. But there's something I couldn't have done without it.