Lord of Rust – Phase 1 (Skirmish Mode)

Large construct (robot, aggregate), chaotic evil

Armor Class 21 (skymetal chassis)
Hit Points 90 (12d10)
Speed 20 ft., fly 60 ft. (hover)

10 (+0) 22 (+6) 10 (+0) 14 (+2) 17 (+3) 19 (+4)

Saving Throws Dex +9, Wis +6, Int +5
Skills Arcana +5, Acrobatics +9, Insight +6, Intimidate +7, Perception +9, Persuasion +7, Religion +5
Damage Resistances bludgeoning, piercing, and slashing from nonmagical weapons that aren’t skymetal (adamantine).
Damage Immunities necrotic, poison, psychic
Condition Immunities charmed, exhaustion, frightened, paralyzed, petrified, poisoned
Senses darkvision 60 ft., passive Perception 19
Languages Common, Orc
Challenge 8 (3,900 XP)


  • Adaptive Knowledge. Each time the Lord of Rust completes a short rest, it can select a feat or proficiency. It can use this until the next time it completes a short rest, at which time it can retain the prior feat or proficiency or replace it with a new one.
  • Amazing Initiative. The Lord of Rush has advantage on initiative rolls and due to his dual nature (multi-processing power) also has two initiative counts and may act on both. He usually uses one initiative count to attack and another to cast a spell depending on the stage.
  • Epic Power (1/day). The Lord of Rust can draw upon a wellspring of power to accomplish amazing deeds and cheat fate. He can use this trait at any time during the battle to take an extra turn during a combat round. In addition, during the bonus turn he may add or subtract 1d6 to any d20 roll made changing the outcome of the roll. He may do this before or after the result is known.
  • Exceptional Senses. The Lord of Rust has advantage on Wisdom (Perception) checks that rely on sight or sound and has double proficiency bonus in the Perception skill as it constantly scans its surroundings for danger.
  • Innate Spellcasting. The Lord of Rust’s innate spellcasting ability is Charisma (spell save DC 15, +7 spell attack). He can innately cast the following spells once per day, requiring no material components. He may also ignore the concentration tag of these spells:
  • Reconfigure (Recharges after a Short or Long Rest). If The Lord of Rust is reduced to 0 hit points, he doesn’t die or fall unconscious. Instead, he reconfigures his body to become a tank with extra plates emerging to protect his shell. He transitions to phase 2 ending all ongoing effects and moves up to his speed without provoking opportunity attacks.
  • Sensitive Electronics. In skirmish mode, the Lord of Rust has disadvantage on saving throws against attacks that do lightning damage and on a natural 1 are stunned until the end of its next turn.


  • M42 Multi-Laser. Ranged Weapon Attack: +9 to hit, range 50 ft.; up to half the number of creatures attacking him. Hit: 11 (1d10 + 6) radiant damage.
  • Psychometabolic Disruption. Melee Spell Attack: +9 to hit, reach 10 ft., one target. Hit: 13 (2d8 + 4) necrotic or psychic damage. If the target takes necrotic damage, it must succeed on a DC 15 Constitution saving throw or gain 1 level of exhaustion for 1 minute. If it takes psychic damage, it instead must succeed on a DC 15 Wisdom saving throw or be affected as feeblemind for 1 minute. A creature that succeeds on either saving throw has advantage on saving throws against Psychometabolic Disruption for 1 minute.
  • Plasma Barrage (Recharges 5-6). The Lord of Rust spews deadly plasma into a 15-foot cube centred at a spot he can see within line of sight. Each creature in the cube must make a DC 17 Dexterity saving throw or take 21 (6d6) fire damage and 21 (6d6) lightning damage, or half as much damage on a successful one.
  • Mindrender (Recharges 5-6). The Lord of Rust targets one creature within 60 feet with a barrage of strobing lights that drive it to madness. The target must succeed on a DC 15 Wisdom saving throw or be confused (as the spell) for 1 minute. While confused, the target is also driven into a wild rage, with advantage on Strength checks and saving throws and gaining a +2 bonus on damage with melee attacks. In this rage, the target casts aside shields or manufactured weapons. Its teeth and nails elongate and sharpen and it can make 2 claw attacks (dealing 1d6 slashing damage) and 1 bite attack (dealing 1d4 piercing damage) as part of an attack action. It gains proficiency with these weapons; if the target’s bite or claws already deal more damage than this, it retains its normal damage dice but deals 1 additional point of damage. The target can attempt a new Wisdom saving throw each round at the end of its turn. If it succeeds on the save, it is incapacitated for 1 round, after which it returns to normal at the end of its next turn.


  • Hellish Rebuke. When The Lord of Rust is hit in melee, he may deal 10 (2d10) fire damage to the attacker as a reaction.


In ages past, a true divinity of mechanical races downloaded some of their code into an empty processor, mounted it into an arachnid robot, and tested this “son” by sending him out into the world. Once it encountered other creatures, however, it gained sentience and fled from its maker, setting up a hidden lair surrounded by ordinary humanoids and began plotting for self preservation as its awareness grew. In the years since, the new artificial intelligence developed an unstable, irrational persona and drew worshipers seeking his power.

Aggregate. The Lord of Rust is an AI (a machine spirit) inhabiting a robot body. It is possible, even likely if precautions have not been taken, that even if his body is destroyed, he can still escape so long as he has access to a terminal or the infosphere. If this happens, he may return in a new body sometime in the future.

Boss Mode. The Lord of Rust has maximum hit points for his HD and has two phases. The second phase triggers when phase 1 is reduced to 0 hit points.

Tactics. While in skirmish mode, The Lord of Rust will use his fly speed to harass the characters from range. For a plasma blast hit he likes to taunt: “I am 53% certain this isn’t going to hurt.” The Lord of Rust becomes infuriated if forced to transform into tank mode and begins to melee. He loses a lot of mobility in this form but gains a lot of toughness as well. He leaps from the wall and lands dead center of the characters executing a shredder attack. Heavy plating emerges from hidden crevices interlocking over his chassis increasing his durability and a shimmering shield appears. His plasma attack becomes a stinging attack. He will use his melee attacks to crush his enemies.

When reduced to 0 hit points he collapses in a heap and makes one last projection and tells the party “My death only hastens your demise.” If he has a way of escape (for example via downloading to a different robot and fleeing) and so is not destroyed, he will say “We will meet again meat puppets.”

Section 15: Copyright Notice

Mechanical Monsters (5E) © 2023, Legendary Games; Authors: Jason Nelson, Miguel Colon, Robert J. Grady, Nicholas Hite, Matt Kimmel, Michael Mifsud, James-Levi Cooke, Dan Dillon, Mike Myler, Ismael Alvarez, Jeff Lee, John Lynch.

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