Keymaster (5e Creature)
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Medium aberration, lawful neutral
Saving Throws Dex +5, Int +7
Advanced Telepathy. The keymaster can perceive the content of any telepathic communication used within 60 feet of it, and it can't be surprised by creatures with any form of telepathy.
Psychic Weapons. The keymaster's weapon attacks are magical. When the keymaster hits with any weapon, the weapon deals an additional 10 (3d6) psychic damage (included in the attack).
Telepathic Shroud. The keymaster is immune to any effect that would sense its emotions or read its thoughts, as well as all divination spells.
Unlock. The keymaster can use a bonus action on its turn to magically unlock a nonmagical lock that it can see and touch with its tail. To unlock a magical lock in this way, it must succeed on an Intelligence (Arcana) check with a DC equal to the DC of the lock.
Multiattack. The keymaster makes four melee attacks.
Scimitar. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) slashing damage plus 10 (3d6) psychic damage.
Keymasters are thin blue-skinned creatures that would look almost identical to humans if not for their four arms and long tails. They have an obsession with locks and keys, cloistering themselves in dusty rooms trying to pick the most complex locks and safes, though if need be, they can open incredibly complicated locks with just a touch from their tails. Rarely do keymasters become criminals, even with their power of unlocking, as they see crime as beneath them, fit only for wretches and fools.
Subterranean Lords. Keymasters usually live alone in majestic underground fortresses carved from stone, though their stony keeps tend to be close to each other. A keymaster will pay dwarves or stone giants handsomely to carve a palace, and with its extremely long lifespan, it can wait for centuries for its eventual completion.