Steel Guardian (5e Creature)
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Large construct, lawful neutral
Keen Sight. The steel guardian has advantage on Wisdom (Perception) checks that rely on sight.
Mirror Carapace. When the steel guardian makes a successful saving throw against a hostile spell, or is missed by a ranged spell attack, the original caster of the spell becomes the spell's new target.
Nanite Swarm. The steel guardian is filled with what looks like glittering silver sand, but is in fact millions of tiny machines which constantly repair the guardian's body. It regains 5 hit points at the start of its turn if it has at least 1 hit point. If the guardian takes acid damage, this trait doesn’t function at the start of its next turn.
On a successful claw attack, the steel guardian injects these nanites into the target's body. Unless the creature also has this ability, it must make a DC 16 Constitution saving throw at the beginning of each of its turns. If the saving throw is successful, the nanites are purged from its body and the effect ends. Otherwise, the target takes 4 (1d8) slashing damage at the end of its turn.
Multiattack. The steel guardian makes four claw attacks.
Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage and the creature is infested by nanites.
Ion Cannon (Recharge 6). The steel guardian fires a beam in a 60-foot line that is 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 28 (8d6) force damage on a failed save, or half as much damage on a successful one.
It is said that in ancient times, when the world faced a terrible calamity, there came a great bird from beyond the sky, which took the people upon its back to find a new world for them to live.
Most people know this as a bedtime story told to children. Few believe that there could be any truth to such an outlandish tale. However, stories are told among the adventurous types of this world, of those who have traveled to the far corners of creation only to be met by invisible walls beyond which lay an ocean of stars... and of those who have traveled into the depths of the world, beyond even the great Underdark, and have found there another world of metal and blinding light.
This world of metal, they say, is patrolled by twelve foot tall, four-armed, eight-eyed demons made of steel - silent guardians who say nothing but protect the secret of the deep, metal world with a murderous ferocity.
A Steel Guardian's Lair
The entirety of the deep world of metal and light is the lair for every steel guardian. The guardians are both individual creatures as well as extensions of the metal world itself, with both interacting with one another.
Steel guardians are never encountered outside the world of metal and light.
On initiative count 20 (losing ties), the steel guardian takes a lair action to produce one of the following effects; the steel guardian can't use the same effect more than once in a row:
The steel guardian calls a nanite swarm from the walls to help repair it, healing 13 (2d8 + 4) health.
The steel guardian activates weapons hidden in the walls to fire bolts of light at its enemies. One creature of the steel guardian's choice is fired at for +7 to hit, and dealing 12 (2d8 + 3) force damage on a hit. Because the attack comes from the nearest wall and not from the guardian, this attack ignores cover and concealment, however the steel guardian must be able to see the creature to target it.