Radiation Elemental

Official Description
"Wretched remains of unfortunate beings lost to the Altar of Corruption. After the Altar's core was destroyed, and its cancerous growth has been stopped, the chunks of the mutated biomass consisting of flesh, remains of the Altar's victims and radioactive material, separated from the radioactive hivemind, started sneaking their way out from the underground confines, each with only one goal to fulfil - to absorb and grow. Emanating radioactive energy, the ghostly radiation elementals, often merging with each other into a larger mass, attempt to absorb any living being and further spread. Possessing a semi-solid form of a fleshy biomass combined with absorbed human and animal bodies, they can reform after being shot or having parts of it blown off as long as at least one nucleus - a bright, glowing, gooey orb making up their core - is intact, or unless they're cleansed with fire."

Trivia

 * They are the only badge exclusive Mutants.
 * The Radiation Elementals could also be inspired by the Necromorphs from Dead Space, like a similar item.
 * They can survive lethal and deadly attacks that would usually kill Mutants, like dismemberment.
 * The Radiational Elementals also have unique variants that are randomized upon spawning as it. This makes it the only morph capable of changing the look every time you spawn as one.