SkullDevil || Skull Island

Skullcrawlers are large serpentine creatures with only two long forelimbs and no hind limbs. Several aspects of their appearance are noticeably skeletal, namely their backs and heads. Their heads closely resemble those of mosasaurs, particularly Tylosaurus. Additionally, the Skullcrawlers have four digits in total on each hand, with the thumb being the smallest digit and the rest of the digits being larger and of the same size. The head of the Skullcrawler is predominantly grey and white in coloration, with the monster's eyes being situated behind two round eye socket-like depressions on the sides of their head. Their pupils are horizontal slits, like those of a goat. the Skull Devil, is almost as tall as Kong himself and possesses distinct spikes on its elbows and a more pronounced, sand-colored transparent ridge running down its spine, along with a wide, flat, crest-like structure on its scalp and a more rounded, crocodilian snout in contrast to the smaller Skullcrawlers' pointed, Tylosaurus-shaped snouts. Close-ups of the creature's face reveal pale green eyes.

The Skullcrawlers are violent and savage creatures that appear to attack and kill anything in sight. Monarch describes them as "hypervores" due to their insatiable appetites, and classifies them more broadly as "destroyers,"[9][19] along with King Ghidorah, Rodan, Scylla, Camazotz, MUTO Prime, Tiamat, and Mechagodzilla. Though most Skullcrawlers seem to act primarily on instinct, the Skull Devil demonstrated some intelligence when it swatted Earl Cole away with its tail before his grenades could detonate. According to The Art and Making of Kong: Skull Island, Skullcrawlers are an invasive species to Skull Island, and live entirely underground, only surfacing to feed.

According to Hank Marlow, Skullcrawlers terrorized Skull Island for thousands of years, forcing the native Iwi tribe to build a huge wall outside of their village to keep them out. To the Iwis' surprise, the giant apes that they once feared began fighting the Skullcrawlers, eventually driving them all underground. The Skullcrawlers remained primarily underground until the seismic charges dropped by the Monarch expedition to the island in 1973 began drawing them back to the surface.

Both Godzilla vs. Kong: The Official Movie Novelization and Godzilla x Kong: Titan Chasers state that the Skullcrawlers evolved from a lineage of non-amniote basal reptilomorphs, with the former adding that they possibly originated from the Hollow Earth. The Kong: Skull Island Cinematic Adventure states that the Skullcrawlers fall under the "sub-division" of Salamandra,[5] suggesting that they are actually amphibians despite their reptilian appearance.

Kong: Skull Island Cinematic Adventure mentions that the Iwi consider the Skullcrawlers to be "servants of some greater evil",[20] but the identity of this greater evil is not specified, if it indeed exists.

The Skullcrawlers are strong enough to prey on Sker Buffalo, as shown in Kong: Skull Island when Kong found one feasting on a carcass. Later on, the individual encountered by the Monarch expedition displayed incredible strength and swiftness, performing a 90-degree turn in a split-second and slamming its tail on the ground forcefully. It additionally shattered a Trikonicorn skull by ramming its head into it. Skullcrawlers possess prehensile triple-forked tongues that can dart from their mouths to wrap around, constrict, or grab prey. Their aim is precise enough to grab a falling soldier in mid-air. The Skull Devil used its tongue to restrain Kong's arm during their fight. The Skull Devil used its prehensile tail to constrict itself around Kong, and was also able to throw Kong with ease using its tail. The smaller Skullcrawlers were able to use their tails as clubs, as demonstrated when one attacked by slamming its tail onto the ground when it confronted the soldiers who were trying to pass through the boneyard. The Skull Devil was more than a physical match for Kong, and it was stated by Hank Marlow to be the beast who killed his parents. The twin .50-caliber Browning M2 aircraft machine guns mounted on the Grey Fox were able to make it bleed, though they did not significantly injure it. The Skull Devil endured a barrage of attacks during its final fight with Kong, mostly notable a boulder and an enormous tree slamming into its face, the ship propeller becoming lodged in its back, being slammed face-first into a mountain, losing one of its eyes to a flare pellet fired by Mason Weaver, and even having its throat slit prior to Kong tearing its innards out.

The Skull Devil was blinded in one eye after Mason Weaver fired a flare gun at it. Kong's makeshift flail embedded the Skull Devil's back when it was thrown, and it was used to slit the beast's throat, causing it to fall limp to the ground momentarily. When the beast used its prehensile tongue to pull Kong's hand, with Weaver held in it, down its throat, Kong mustered all of his strength to pull his hand free of the Skull Devil's gullet, disemboweling it. Mechagodzilla killed Number 10, a giant Skullcrawler, before it could land a hit, grabbing the beast by its arms and splitting it in half with the Proton Scream at 40% power.