Organization- Acid Mutant

And the images they saw were of chaos and death. Sitterson had just seen a lab worker with whom he’d sometimes enjoyed drinking taken down by a mutant, thrashing as the stick-thin red thing held his arms and vomited onto his face and head. After an instant of motionless shock the man had started writhing and kicking as wisps of smoke rose from his eyes, mouth, and nose, and his head began to melt.

The mutant had sat back for a while, and then it commenced feeding.

- The Cabin in the Woods: The Official Movie Novelization, chapter 11