Crystal Golem (Crystalline Sorcerer)

Berserk: When the golem starts its turn with half its hit points or fewer, it goes berserk. On each of its turns while berserk, the golem attacks the nearest creature it can see. If it can't preceive any other creatures on its turn, the golem will attack the cloest 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.

The golem's creator or the creator's chosen allies, if within 60 feet of the berserk golem, can try to calm it by speaking firmly and persuasively. The golem must be able to hear them, who must then take an action to make a DC 20 charisma (persuasion check). If the check succeeds, the golem ceases being berserk. If it takes damage while still at 40 hit points or fewer, the golem might go berserk again.

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

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

Multiattack. The golem makes 2 slam (or Crystal Sword attacks if avaliable) attacks.

Slam. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) bludgeoning damage plus 4 (1d8) piercing damage. 

Crystal sword. Melee weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 5) slashing damage plus 4 (1d8) force damage. This action is only useable if its using the active crystal node in the crystal assimilation feature.

Reflective Blast (Uses the spell slots of the host): The golem gathers the magical power from its creator inside it to fire off an explosion of pure magic. The golem absorbs up to 4 spell slots from its creator (must add up to level 4 or higher) and chooses a point with 60 feet. Each creature within 30 feet of that point must a dexterity saving with a DC equal to its creator's spell casting modifier, taking 68 (8d8) force damage on a failed save, or half as much damage on a successful one. This action is only useable if its using the active crystal node in the crystal assimilation feature.

Crystal Assimilation. Whenever the golem is within 30 feet of at least one crystal node (Subclass feature) that was left on the field by its creator, it may use an action to assimilate up to 2 nodes into itself in order to boost its power. The golem may then choose what the node will activate, choosing between gaining the Reflective Blast action or Crystal Sword attack. If both nodes are successfully assimilated, the golem gains access to both actions.

Node Realignment. If the golem only has one node assimilated, it may then use a bonus action to switch the active node between the Reflective Blast Action and Crystal Sword Action. If both nodes are successfully assimilated, the golem may use a bonus action to gain 4 (1d8) Temporary Hitpoints.