>>42391208desu I would've gone with;
> Regivolt [Electric]Based on Lodestones and Magnetism, it would appear as central core body with metallic filaments creating its limbs, the body would have static electricity bouncing off it causing the filaments to vibrate in a wave formation while also causing luminous structures on the central body to glow.
> Regignis [Fire]Central body would be shaped like a volcano with a cone-like shape, and vents coming off its sides where fumes emanate from (similar to Torkoal's hump), arms and legs would be made of molten rock some of which is partially solidified particularly towards the extremities giving a layered appearance to the fingers and toes. Back of the body might also have an indented shape referencing the ability for Volcanoes to collapse on themselves.
> Regibrim [Poison]Body would be made of a mixture of Sulfur and Lead-like minerals in visual design giving it a distinct yellow-grey colour combination, around its eyes would be the radioactive symbol comprised of yellow minerals suspended within the grey mineral. The body would have small craters across it and where the craters were facing correctly there would be pools of an acid liquid that would've formed. The arms and legs would appear similar to mercury and appear from holes within the Pokemon's central body with shoulder-like crests, sometimes the sulfur minerals would surface in the arms and legs of the Pokemon in its idle.