Mantellum has a cloak and a tail that coils behind him, making him look like a human manta ray whose folds drape over the surrounding area.
Abilities and Powers
Mantellum's area-of-effect power creates increasingly protective layers that block perception powers by blinding shards. This even affects subconscious ones such as Lung's transformation, and human senses. This effect is so intensive that it blocks even Contessa's power, although it does not work across dimensional boundaries, or video.
According to Cauldron records, his power nullifies powers within 15 feet of him and senses within 5 feet, but during the Irregulars' raid, his power's radius was around 100 feet thanks to workarounds devised by Weld and the other Irregulars.
Mantellum was Cauldron test subject 2601. Because Cauldron thought that his powers were not developing, they released him into Earth Bet, and he was termed a Case 53.
Mantellum accompanied the Irregulars on their raid on Cauldron's headquarters to foil Contessa and the Custodian, whose abilities his power blocked, while other Irregulars cornered Doctor Mother downstairs from their entrance. His power nullification forced Contessa to escape the facility through a dimensional portal and fake her own death at the hands of another Irregular. Meanwhile, the Custodian led Weaver's group to Mantellum's blind spot, where Weaver used her swarm to kill him with Defiant's nano-thorn knife.
↑Mantellum Case 53. Blocks out sensory aspects of powers progressively more with proximity. Irregulars - Parahuman List, bolded edit by Wildbow.
↑Mantellum operates in a different way than Hatchet Face, blocking all power use into or out of his radius. It becomes a contest of strength. Make your decision accordingly. - Reddit comment by Wildbow
How do you nullify a power in Wormverse? Would any old power nullifier from another universe work, or does it need to be done in a specific way? Similarly, what would it take to duplicate a Wormverse power? Mantellum was a power nullifier who basically blinded shards. He arguably wouldn't have any effect on a sensory power that wasn't a Worm power. - Comment by Wildbow on Reddit
↑With Contessa, we found a possible in, a weak Case Fifty-Three that Thinkers couldn’t see clearly, we helped him get stronger, mostly by giving him a chance to figure out how it worked, and then we moved fast. - Excerpt from Radiation 18.9
↑People were reacting, outside the circle. How much damage had I done?
The lights went out.
Mantellum’s effect dissipated. The blind spot filled in, a crowd, capes, blood spraying. My bugs could sense them all. - Excerpt from Venom 29.5