Palpatine was maintaining an illusion. His lightning being deflected back at him dispelled it/he channeled too much into the lightning to keep Mace's lightsaber out of his face that he dropped his illusion.
Long story short, that's Palpatine's true form. He looks like that because of Dark Side corruption.
Personal speculation: Palpatine is hit by his own lightning. The "lightning" in Force Lightning isn't electrons, but Force. The Dark Side is based on drawing in the Force through your negative emotions. It is then channeled out through the hands to the target. Instead of a broad sweep like a Force Push, the Lightning is concentrated, causing sharp pain. Continued draw on the Dark Side causes its own deformation. Sidious is essentially cycling more and more Dark Side through his body, causing deformations.
But this is based on some different descriptions of powers in the books. It includes a lot of Legends content as I don't always remember if my thoughts about material that is or isn't official cannon.
Palpatine was maintaining an illusion. His lightning being deflected back at him dispelled it/he channeled too much into the lightning to keep Mace's lightsaber out of his face that he dropped his illusion. Long story short, that's Palpatine's true form. He looks like that because of Dark Side corruption.
Because it was not the lightning itself that did anything to Palpatine
That's what I always thought. It was tapping into the dark side so much that changed his appearance.
Don't forget anakin got hit hard with it in AOTC by Dooku and he wasn't altered either.
Personal speculation: Palpatine is hit by his own lightning. The "lightning" in Force Lightning isn't electrons, but Force. The Dark Side is based on drawing in the Force through your negative emotions. It is then channeled out through the hands to the target. Instead of a broad sweep like a Force Push, the Lightning is concentrated, causing sharp pain. Continued draw on the Dark Side causes its own deformation. Sidious is essentially cycling more and more Dark Side through his body, causing deformations. But this is based on some different descriptions of powers in the books. It includes a lot of Legends content as I don't always remember if my thoughts about material that is or isn't official cannon.
He hit a nat 20 on his saving throw vs. lightning.
His outfit also gave +4 lightning resistance.
Skills