Rot Locust (5e Creature)
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Gargantuan fiend, chaotic evil
Saving Throws Str +14, Con +14
Decay Aura. At the start of each of the locust's turns, each creature within 5 feet of it takes 10 (3d6) necrotic damage. Any nonmagical weapon that hits the locust corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition that hits the locust is destroyed after dealing damage.
Multiattack. The locust makes four attacks, only one of which may be with its bite.
Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 30 (4d10 + 8) piercing damage, plus 28 (8d6) necrotic damage.
Slam. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 30 (4d10 + 8) bludgeoning damage, plus 28 (8d6) necrotic damage. In addition, nonmagical armour worn by the target is partly decayed and takes a permanent and cumulative -1 penalty to the AC it offers. The armour is destroyed if the penalty reduces its AC to 10.
Spawn of the Devourer (1/Day). The locust magically calls 2d4 swarms of insects. Each swarm has a 30 percent chance of being a variant swarm (if a swarm is a variant, the locust chooses what kind it is). The called creatures arrive in 1d4 rounds, acting as allies of the locust and obeying its spoken commands. The beasts remain for 1 hour, until the locust dies, or until the locust dismisses them as a bonus action.
Rot locusts are titanic insect-like fiends that are masters of rot and decay, and can summon ravenous beasts and oozes. Their touch can destroy almost everything. Wood rots into dust within moments, stone cracks and disintegrates, and metal rusts into uselessness. They have no feelings but hatred and a lust for destruction, and they aim to choke out and end all light and good in the multiverse. They especially hate religious places like shrines and temples, destroying any they discover before devouring their occupants.