Immutable Form. The Sentinel is immune to any spells that would alter its form.

Overcharge. When the Sentinel takes lightning damage it may recharge its Electric Blast.

Magic Weapon. The Sentinel Attacks are considered Magical for the point of overcoming resistance.

Magic Resistance. The Sentinel gets advantage on Saving Throws against magical effects.

Self-Repair. Every turn this creature regains 1d6 hit points unless it takes thunder.

Multiattack. The guardian makes two Trauma Arm attacks.

Trauma Arm. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (1d6 + 4); bludgeoning damage plus (2d6) Lightning damage.

Discharge (recharge 5-6). A rupture of electricity explodes in a 10ft radius. All creatures in the radius must make a dexterity saving throw or take (5d8) Lightning damage on a failed save or half as much on a successful one. If the creature is wearing metal they make the check at disadvantage.

Internal Realignment. When the Sentinel takes damage from a certain type of damage it may use its reaction to gain resistance till the end of the next turn.