Utilizing Soul Multiplicity, the user combines numerous souls with weak rejection to create one body. This manifests a highly stable and extremely strong transfigured human that doesn't speak and has little to no chance of dying off on its own.
A Polymorphic Soul Isomer is an attack specialist with explosive power behind its hits. This is due to Soul Multipilicty expending numerous souls to create it. However, the trade-off for is extraordinary strength is its lack of durability. A Polymorphic Soul Isomer can be killed with a single direct hit using cursed energy.
Mahito first created a Polymorphic Soul Isomer during his fight with Yuji and Aoi Todo in Shibuya. It was used as a distraction to keep Aoi Todo at bay so Mahito could focus on fighting Yuji one on one.
Todo initially underestimated the Polymorphic Soul Isomer, believing it to be ranked around the level of a just grade 2 or 3 cursed spirit. Upon being struck by one of them, Todo was surprised to find it had enough strength to hit him clean through a building.
The grade 1 sorcerer used his innate technique to outmaneuver the transfigured human and smashed its head with a cursed energy infused punch. Todo was further surprised to find that the Polymorphic Soul Isomers are fragile enough to be defeated with a single hit.
Two more Polymorphic Soul Isomers confronted Todo after he defeated the first one, but he made short work of them after learning their weakness. Mahito believed they would do the trick and was disappointed when Todo defeated them so quickly.
While heavily injured after being hit with Black Flash, Mahito created a Polymorphic Soul Isomer to fend off Yuji. The Polymorphic Soul Isomer and Yuji rapidly parried each other's punches until the latter put it down with a kick. Although once again easily defeated, the Polymorphic Soul Isomer bought Mahito enough time to ascend into his true form, the Instant Spirit Body of Distorted Killing.