I had this idea when I noticed a spell called crAbVampire in creation kit.
(crAbVampire gives 50% resistance to frost and 50% weakness to fire)
voice: dlc1maleVampire
class: EncClassVampire
keywords: vampire
combat style: csVampireMagic
Features:
a lvl 20 crab,
drops dawnguard armor
Other:
Despite having a vampire drain spell, being a vampire class, and having a vampire combat style, the crab will only attack with its claws. I don't know if there is a way to let it use magic while still being a mudcrab.
Special thanks to Linthar for More Informative Console
(crAbVampire gives 50% resistance to frost and 50% weakness to fire)
voice: dlc1maleVampire
class: EncClassVampire
keywords: vampire
combat style: csVampireMagic
Features:
a lvl 20 crab,
drops dawnguard armor
Other:
Despite having a vampire drain spell, being a vampire class, and having a vampire combat style, the crab will only attack with its claws. I don't know if there is a way to let it use magic while still being a mudcrab.
Special thanks to Linthar for More Informative Console