Ancient Machina

Magitech Core. Once per turn as a free action the Ancient Machina can choose a type of  damage and whenever the Ancient Machina takes the chosen damage  ( Cold, Lighting , Fire , Force , Necrotic , Radiant)  it takes no damage and instead regains a number of hit points equal to the chosen damage dealt. If hit with an opposing damage from the table below all damage is doubled , unless force is the chosen damage, If so all force damage done to The Ancient Machina is doubled and all force damage The Ancient Machina makes is doubled. Damage type can not be changed until a Magitech Core Overload.

Cold- Lighting , Fire 

Necrotic - Radiant 

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

Multiattack. The golem makes two attacks

Slam. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 20 (3d8 + 7) bludgeoning damage + 1d6 Magitech Core damge type.

Magitech Core Overload(Recharge 6). The Ancient Machina explodes its magitech  energy in a 15-foot radius with The Ancient Machina at the center  . Each creature in that area must make a DC 15 Dexterity saving throw, taking (10d6) Magitech Core damage on a failed save, or half as much damage on a successful one.