Lord of Rust – Phase 2 – Tank Mode

Large construct (robot, mythic, aggregate), chaotic evil

Armor Class 18 (hardened skymetal chassis)
Hit Points 90 (12d10) plus 40 hp force field.
Speed 20 ft., climb 40 ft.

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

Saving Throws Str +9, Wis +6, Int +5
Skills Arcana +5, Athletics +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. As in skirmish mode.
  • Amazing Initiative. As in skirmish mode.
  • Battle-hardened. In tank mode, the Lord of Rust has a damage threshold of 5, reducing damage from all attacks by 5.
  • Epic Power (1/day). As in skirmish mode.
  • Exceptional Senses. As in skirmish mode.
  • Force Field. A shimmering shield of energy engulfs The Lord of Rust’s chassis granting extra hit points. The shield regenerates to full so long as it has 1 hit point at the start of his turn. While the shield is up, he is immune to lightning, force and critical hits. Once it is exhausted these immunities disappear and the shield collapses ceasing to regenerate. In addition, on exhaustion, it discharges in a ball of thunder and lightning dealing 10 (4d4) lightning damage and 10 (4d4) thunder damage in a 20-foot-radius sphere centered on The Lord of Rust. A DC 11 Dexterity saving throw reduces this damage by half.
  • Innate Spellcasting. As in skirmish mode. Any spells it has already cast in skirmish mode are replenished when the Lord of Rust switches to tank mode.
  • Spider Climb. The Lord of Rust can climb difficult surfaces while in tank mode, including upside down on ceilings, without needing to make an ability check.


  • Multiattack. The Lord of Rust releases one Spiderbot Swarm until he has no more, and then makes three attacks: two with his Pincer and one with Megabot Sting.
  • Pincer. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 14 (2d8 + 6) bludgeoning damage. If the target is Large or smaller, it is grappled (escape DC 16). Until this grapple ends, the target is restrained; The Lord of Rust automatically does 14 (2d8 + 6) damage until the grapple is broken. While crushing an opponent, he losses a claw attack.
  • Megabot Sting. Melee Weapon Attack: +9 to hit, each 5 ft.; one creature. Hit: 11 (1d10 + 6) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 22 (4d10) poison damage from a pharmaceutical based neurotoxin on a failed save, or half as much damage on a successful one.
  • Shredder (Recharges after a Long Rest). The Lord of Rust lands in the middle of a group he can see within his lair in a whirlwind of razor-sharp legs. Every creature in a 30-foot sphere centered on him must make a DC 11 Dexterity saving throw taking 20 (5d8) slashing damage on a failed save, or half as much damage on a successful one.
  • Spiderbot Swarm (Recharge 5-6 once all swarms exhausted). The Lord of Rust has a number of spiderbot swarms equal to the number of characters attacking him attached to his underbelly, which he can release into combat. The swarm appears in an unoccupied space within 5 feet of The Lord of Rust and acts as an ally. It remains for 10 minutes, until it or it’s the Lord of Rust dies, or until he recalls the swarm as an action.
  • Mindrender (Recharges 5-6). As in skirmish mode.


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


The Lord of Rust lairs in a gargantuan spherical room made of metal. At the center of the room a massive wheel lined with sharp edges forms a floor of sorts at the centre of the sphere. The wheel spins slowly and does not extend all the way to the sphere. Below is darkness. A latticework of metal girders connects to the wheel. The whole of the device comprises a long mechanical arm ending in a metal wheel far larger than any mill’s waterwheel. During both stages he has access to the following Lair Actions.

On initiative count 20 (losing initiative ties), The Lord of Rust takes a lair action to cause one of the following effects, He can’t use the same effect two rounds in a row:

  • Automated Cannons pop out of cunningly hidden recesses in the roof and spray the area with gunfire.
  • They are superhumanly accurate and only hit enemy creatures. Each creature in the room must make a DC 15 Dexterity save or take 12 (4d6) piercing damage.
  • The room is flooded with tear gas. All creatures that breath must make a DC 15 Constitution saving throw or until the end of their next turn they are immobilized as they start heaving and retching violently.
  • The Lord of Rust may cast a spell.


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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