Arcane Golem

Berserk. Whenever the golem starts its turn with 40 hit points or fewer, roll a d6. On a 6, the golem goes berserk. On each of its turns while berserk, the golem attacks the nearest creature it can see. 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.

The golem’s creator, 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 its creator, who must take an action to make a DC 15 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.

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.

Topaz Spell Gem. The golem has 3 Topaz Spell Gems, each containing a 4th level Spell. The spells in the gem have +10 to hit and a DC 17.

1/day. Fire Shield, Staggering Smite, Confusion

Multiattack. The golem makes two slam attacks it can also replace a slam attack with a rune blast

Slam. Melee Weapon Attack: +7; to hit, reach 5 ft., one target. Hit:  (2d8 + 4) bludgeoning damage.

Ice Rune. Ranged Attack: +7; to hit, 120ft; one target. Hit: (3d8+4) cold damage.

Rune Blast . The golem activates the runes on its body creating a effect. Each time the golem activates a rune roll a 1d6 to see what rune is activated.

1-Fire Rune- A rune ignites on the golems hand shooting flames out in a 20ft cone. Each creature in the cone must make a DC 14 Dexterity save or take 6d4 fire damage, creatures that pass take half damage. When a creature fails they are ignited and take 1d4 fire damage at the start on their next turn,

2-Ice Rune- A rune freezes over the golems hand and blasts and icicle outward from its hand toward a creature it can see within 120ft. Refer to the Ice Rune attack

3-Lightning Rune- Electricity shoots out from the golems hand in a 5ft wide 120ft line, each creature in the line must make a DC 14 dexterity saving throw or take 12d4 lightning damage and also lose their reaction. Creatures that pass take half damage and does not lose their reaction.

4-Force Rune- A wave of pure magical force blasts around its body, each creature within 10ft of the golem must make a DC 14 constitution saving throw or take 4d4 force damage and pushed back 20ft and fall prone. If the creature that is pushed hits another creature, the creature they slam into takes 2d6 bludgeoning damage and also falls prone. If a creature passes the save they take half damage and are not pushed.

5-Necrotic Rune- A wave of black necrotic energy blasts outward from its body. Each creature within 60ft of the golem must make a DC 14 constitution saving throw or takes 3d4 necrotic damage or 5d4 necrotic damage if the creature does not have all of its hit points. The golem heals for half the damage dealt.

6-Radiant Rune- A blast of blind light shoots from the gems on its body toward 3 creatures the golem can see within 120ft. Each creature must make a DC 14 dexterity saving throw or take 4d6 radiant damage and be blinded until the end of their next turn, if the creature passes they take half damage and are not blinded. If a creature is invisible within 60ft of the golem, they become revealed

The Arcane Golem has 2 legendary actions per round that can be used to do any of the following things;

Slam (1 cost). The golem makes a slam attack

Move (1 Cost). the golem moves up to half its movement speed without provoking opportunity attacks

Activate Rune (2 Cost). The golem uses its Rune Blast.