Clay Wizard

Acid Absorption. Whenever the golem is subjected to acid damage, it takes no damage and instead regains a number of hit points equal to the acid damage dealt.

Berserk. Whenever the golem starts its turn with 60 hit points or fewer, the golem goes berserk. On each of its turns while berserk, the golem attacks the nearest creature it can see provided a more powerful clay creature does not give a command. If no creature is near enough to move to and attack, the golem attacks an object, with preference for an object smaller than itself. Once the golem goes berserk, it continues to do so until it is destroyed or regains all its hit points. While the golem is berserk it cannot cast spells except for the shield and absorb elements spells.

Immutable Form. The golem is immune to any spell or effect that would alter its form.

Magic Resistance. The golem has advantage on saving throws against spells and other magical effects.

Magic Weapons. The golem’s weapon attacks are magical.

Regeneration. The troll regains 30 hit points at the start of its turn. If the troll takes fire damage, this trait doesn't function at the start of the troll's next turn. The troll dies only if it starts its turn with 0 hit points and doesn't regenerate.

Innate Spellcasting. The Clay Wizard's innate spellcasting ability is Intelligence (spell save DC 20, +9 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

At will: detect evil and good, detect magic, disguise self, mold earth, mending, chill touch

6/day each: blur, hold person, 

6/day each: counterspell, tongues, melf's minute meteors, erupting earth, dispel magic

10/day each: shield, absorb elements, magic missile

4/day each: polymorph, blight

1/day each: disintegrate, finger of death

Metamagic. The Clay Wizard has a total of 9 sorcery points to spend on meta magic abilities from the sorcerer class.  These include subtle spell, empowered spell, and heightened spell

Multiattack. The golem makes two slam attacks.

Slam. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 6) bludgeoning damage. If the target is a creature, it must succeed on a DC 15 Constitution saving throw or have its hit point maximum reduced by an amount equal to the damage taken. The target dies if this attack reduces its hit point maximum to 0. The reduction lasts until removed by the greater restoration spell or other magic.

Haste. This ability is only available in berserk mode. Until the berserk mode ends, the golem magically gains a +2 bonus to its AC, has advantage on Dexterity saving throws, and can use its slam attack as a bonus action.