Lairon (5e Creature)
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Medium elemental, any alignment
Siege Monster. The lairon deals double damage to objects and structures.
Heavy Metal. The lairon has advantage on saving throws to resist being forced to move.
Iron Head. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 17 (4d6 + 3) bludgeoning damage.
Rock Slide. Ranged Weapon Attack: +1 to hit, range 60/180 ft., one target. Hit: 6 (2d6 - 1) bludgeoning damage.
After its shocking transformation from a humble aron, the lairon has a much sturdier frame forged from metal, which it can use to bludgeon its opponents into unconsciousness, but it prefers to be kind to its fellow creatures and to help the environment in which it resides until it eventually evolves into the unconquerable aggron.