The Revenant appears to be stitched together remains of various corpses with no care for how they would look and infused with the Uroboros virus that manifests itself into a core, which acts as the creature's weakspot.
The Revenants, Slingers, Splashers and Durgas are never seen alongside the Rotten or other t-Phobos creations, except one instance with a Glasp, which was hidden from them. This suggests that, like earlier Uroboros creatures such as Reapers, they are hostile towards members of all other species. This is supported by the fact that the first time a Revenant is sighted in the main campaign, it is standing over and attacking a mutilated corpse that was likely a recently dead Rotten.
Tada, Takuji, ed (2015). BIOHAZARD REVELATIONS 2 ULTIMANIA. Square Enix.