Composite Golem

Melee Weapon Attack: your spell attack modifier to hit, reach 5 ft., one target you can see. Hit: 1d8 + PB bludgeoning damage.

When the golem takes lightning damage, it gains temporary hit points equal to the damage it takes. As part of the same reaction, a creature within 30 feet of your golem must succeed on a Dexterity saving throw against your artificer spell save DC or take lightning damage equal to the temporary hit points gained. On a success, the creature takes half as much lightning damage.