Originally Posted by Hanuman
Frankenstein is a flesh golem, there are rules for that.
Nitpick: Frankenstein was a human.
Flesh golems were inspired by his monster, but his monster is not a flesh golem. A flesh golem is a perfectly valid means to replicate the classic Frankenstein's monster in D&D, but the two are functionally different.
Flesh golems are animated by an elemental spirit through rituals and carry a magic immunity.
Frankenstein's monster was animated through electric shock (believed at some points to be the essence of life) with abuse of science, and shows no indication of being immune to magic.
The only thing they really share is that they're made of multiple dead bodies. There are many undead that are essentially the same thing. It's the animating force that matters. Undead if it's negative energy, construct (golem) if it's elemental, construct (robot) if it's mechanical/no-magic electrical.