Source: Tasha's Cauldron of Everything

Wondrous item, artifact (requires attunement)

Named for the warlord who infamously employed it, the Mighty Servant of Leuk-o is a fantastically powerful, 10-foot-tall machine that turns into an animate construct when piloted. Crafted of a gleaming black alloy of unknown origin, the servant is often described as a combination of a disproportioned dwarf and an oversized beetle. The servant contains enough space for 1 ton of cargo and a crew compartment within, from which up to two Medium creatures can control it — and potentially execute a spree of unstoppable destruction.

Tales of the servant's origins involve more conjecture than fact, often referring to otherworldly beings, the mysterious Barrier Peaks in Oerth, and the supposedly related device known as the Machine of Lum the Mad. The best details on the device's origins and operation can be found in the Mind of Metal, a tome of artificer's secrets that connects the device to the traditions of the lost Olman people, and which was written by Lum the Mad's several times over granddaughter, Lum the Maestro, while she reconstructed the long disassembled Mighty Servant of Leuk-o.

Dangerous Attunement. Two creatures can be attuned to the servant at a time. If a third creature tries to attune to it, nothing happens.

The servant's controls are accessed by a hatch in its upper back, which is easily opened while there are no creatures attuned to the artifact.

Attuning to the artifact requires two hours, which can be undertaken as part of a long rest, during which time you must be inside the servant, interacting with its controls. While crew members are attuning themselves, any creature or structure outside and within 50 feet of the servant has a 25 percent chance of being accidentally targeted by one of its Destructive Fist attacks once during the attunement. This process must be undergone every time a creature attunes itself to the artifact.

Controlling the Servant. While any creatures are attuned to the artifact, attuned creatures can open the hatch as easily as any other door. Other creatures can open the hatch as an action with a successful DC 25 Dexterity check using thieves' tools. A Knock spell cast on the hatch also opens it until the start of the caster's next turn.

A creature can enter or exit through the hatch by spending 10 feet of movement. Those inside the servant have total cover from effects originating outside it. The controls within it allow creatures to see outside without obstruction.

While you are inside the servant, you can command it by using the controls. During your turn (for either attuned creature), you can command it in the following ways:

  • Open or close the hatch (no action required, once per turn)
  • Move the servant up to its speed (no action required)
  • As an action, you can command the servant to take one of the actions in its stat block or some other action.
  • When a creature provokes an opportunity attack from the servant, you can use your reaction to command the servant to make one Destructive Fist attack against that creature.

While there are no attuned creatures inside the servant, it is an inert object.

Ghost in the Machine. Upon his death, the soul of the mighty warlord Leuk-o was drawn into the artifact and has become its animating force. The servant has been known to attack or move of its own accord, particularly if doing so will cause destruction. Once every 24 hours, the servant, at the DM's discretion, takes one action while uncrewed.

If the servant loses half of its hit points or more, each creature attuned to it must succeed on a DC 20 Wisdom saving throw or be charmed for 24 hours. While charmed in this way, the creature goes on a destructive spree, seeking to destroy structures and attack any unattuned creatures within sight of the servant, starting with those threatening the artifact — preferably using the servant, if possible.

Self-Destruct. By inputting a specific series of lever pulls and button presses, the servant's two crew members can cause it to explode. The self-destruct code is not revealed to crew members when they attune to the artifact. If the code is discovered (the DM determines how), it requires two attuned crew members to be inside the servant and spend their actions on 3 consecutive rounds performing the command. Should the crew members begin the process of entering the code, though, the servant uses its Ghost in the Machine property and turns the crew members against each other.

If the crew members successfully implement the code, at the end of the third round, the servant explodes. Every creature in a 100 foot-radius sphere centered on the servant must make a DC 25 Dexterity saving throw. On a failed save, a creature takes 87 (25d6) force damage, 87 (25d6) lightning damage, and 87 (25d6) thunder damage. On a successful save, a creature takes half as much damage. Objects and structures in the area take triple damage. Creatures inside the servant are slain instantly and leave behind no remains.

This does not destroy the servant permanently. Rather, 2d6 days later, its parts — left arm, left leg, right arm, right leg, lower torso, and upper torso — drop from the sky in random places within 1,000 miles of the explosion. If brought within 5 feet of one another, the pieces reconnect and reform the servant.

Destroying the Servant. The servant can be destroyed in two ways. After it has self-destructed, its disconnected pieces can be melted down in one of the forge-temples of its ancient Olman creators. Alternatively, if the servant strikes the Machine of Lum the Mad, both artifacts explode in an eruption that is three times the size and three times the damage as the servant's Self-Destruct property.

Mighty Servant of Leuk-o
Huge Construct
Armor Class 22 (natural armor)
Hit Points 310 (27d12 + 135)
Speed 60 ft.
30 (+10) 14 (+2) 20 (+5) 1 (-5) 14 (+2) 10 (+0)
Saving Throws: Wis +9, Cha +7
Skills: Perception +9
Damage Resistances: piercing, slashing
Damage Immunities: acid, bludgeoning, cold, fire, lightning, necrotic, poison, psychic, radiant
Condition Immunities: all conditions but invisible and prone
Senses: blindsight 120 ft., passive Perception 19
Languages: understands the languages of creatures attuned to it but can't speak
Proficiency Bonus: +7
Immutable Existence. The servant is immune to any spell or effect that would alter its form or send it to another plane of existence.
Magic Resistant Construction. The servant has advantage on saving throws against spells and other magical effects, and spell attacks made against it have disadvantage.
Regeneration. The servant regains 10 hit points at the start of its turn. If it is reduced to 0 hit points, this trait doesn't function until an attuned creature spends 24 hours repairing the artifact or until the artifact is subjected to lightning damage.
Standing Leap. The servant's long jump is up to 50 feet and its high jump is up to 25 feet, with or without a running start.
Unusual Nature. The servant doesn't require air, food, drink, or sleep.
Destructive Fist. Melee or Ranged Weapon Attack: +17 to hit, reach 10 ft. or range 120 ft., one target. Hit: 36 (4d12 + 10) force damage. If the target is an object, it takes triple damage.
Crushing Leap. If the servant jumps at least 25 feet as part of its movement, it can then use this action to land on its feet in a space that contains one or more other creatures. Each of those creatures is pushed to an unoccupied space within 5 feet of the servant and must make a DC 25 Dexterity saving throw. On a failed save, a creature takes 26 (4d12) bludgeoning damage and is knocked prone. On a successful save, a creature takes half as much damage and isn't knocked prone.