Frost Giant Everlasting One (VgtM)
Frost giants live in a “Might makes Right” based society, where leadership is established by how many skulls you can bash. Unfortunately, even for a giant, natural strength of arms can only take one so far. Many resort to other means to augment their battle prowess, from powerful items to spells. The Frost Giant Everlasting One is a giant that has been “blessed” by the god Vaprak, granting them a trollish temperament and trollish regeneration, partially thanks to eating an entire troll. As expected, this gives them quite the advantage in battles against Frost Giants, because they don’t typically wield fire. Should an Everlasting one lose the blessing of Vaprak, their regeneration goes haywire, growing tumors, digits, limbs, even extra heads.
Aside from simply having a bigger and beefier giant to smash your PCs, this could be a buy in for the realm of political meddling. The players might want a particular giant to rule the tribe so they can form an alliance, only for the Everlasting One to stand in the way.
In combat, the Everlasting One is basically a Barbarian. They rage, they rush in, they smash. As an alternative to attacking with their Greataxe, they are specialized in grappling, but unfortunately have no particular synergies to use once they grab ahold of someone. In order to capitalize on that particular tactic, you should have hazards for the giant to throw people into. Unlike PC Barbarians, the Everlasting One has a competent ranged attack, the good old Rock, which they can even Multiattack with. Every Everlasting One has a 25% chance to have an extra head, granting them advantage on perception checks and a bunch of saving throws. To really show the idea of them regenerating “wrongly” consider having one grow an extra head during combat.
In the changeover, the Everlasting one had their Rock attack appended to their Multiattack.