Axiomatic Mind. The monodrone can’t be compelled to act in a manner contrary to its nature or its instructions.

Disintegration. If the monodrone dies, its body disintegrates into dust, leaving behind its weapons and anything else it was carrying.

Multi-Spectrum Sensors (90 ft.). The monodrone can see normally in darkness and magical darkness, can see invisible objects and creatures, and can automatically detect visual illusions and succeed on saving throws against them. The monodrone can see heat and other forms of radiation outside of a humanoid's visible spectrum. The monodrone can also "see" sound waves and vibrations. The monodrone can see through most barriers and target creatures through even complete cover (treat cover as 1 level lower than normal for the purpose of attack rolls) but is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt. Beyond 90 ft., the monodrone can see as well as an average humanoid.

Magic Resistance. The monodrone has advantage on saving throws against spells and other magical effects.

Field Promotion. When a Modron is destroyed or promoted, the nearest Modron of the next rank down is immediately compelled to upgrade itself and fill the gap. The Modron begins upgrading at the start of its next turn, and completes 1 round of upgrades at the start of its next turn after that. The upgrading process takes 1 round for each rank above monodrone that the Modron is upgrading into. During this process, the Modron is incapacitated and keeps all of its current stats and conditions until the upgrade is complete. Once the upgrade is complete, the Modron emerges in its upgraded form with full hit points and no conditions.

Force Field. An invisible wall of force springs into existence within 10 feet of the monodrone. The wall appears in any orientation the monodrone chooses, as a horizontal or vertical barrier or at an angle. It can be free-floating or resting on a solid surface. The wall can be a flat 5 ft. by 5 ft. square barrier, or it can form a cube with side lengths of 1 foot. The thickness of the wall is always 1/4 inch. If the wall cuts through a creature's or object's space when it appears, the obstruction is pushed to one side of the wall as the monodrone chooses. The barrier provides total cover and nothing can physically pass through it. The force field is destroyed if takes more than 10 points of physical, force, or thunder damage at once, or more than 5 points of lighting damage at once, if it carries more than 1,000 lb., or if the monodrone maintaining it takes any damage or moves more than 10 feet away from it. If the monodrone moves, the force field moves with it. If the force field encounters an obstacle while moving this way, the monodrone will be unable to move further without repositioning the force field around the obstacle. As a Bonus Action, the monodrone can reposition the force field anywhere within 10 feet of itself. If the force field encounters an obstacle, it wins all pushing contests against creatures but is stopped by an object weighing more than 1,000 lbs. (or something equivalently immobile). The force field exists as long as the monodrone wishes, unless it is destroyed. As long as the force field exists, the monodrone cannot take any Actions.

Parallel Processing. The monodrone attempts to link with nearby monodrones to synchronize efforts and share energy. Any monodrone within 10 feet who takes this action can link with this monodrone, and the link extends to any additional monodrones linked to either of them. While linked, the monodrone with the highest initiative is made the link leader, and all other monodrones in the link can't do anything while the link is active. The link leader's Force Field ability has all of its numbers (except for the 1/4 inch thickness) multiplied by the number of monodrones in its link. At the start of its turn, the link leader can separate any part of his link, link with another willing link leader, or transfer leadership to another monodrone in its link. If a monodrone in a link is destroyed or drops out of the link, the link separates into smaller links so that there are only unbroken chains of monodrones with no more than 10 feet between them. If an active Force Field or Laser extends outside the range of the new link, it disappears. If the link leader is destroyed, leadership instantly transfers to the monodrone with the highest initiative in the link.

Grappling Claw. Melee or Ranged Weapon Attack: +3 to hit, reach 5 ft. or range 30/90, one target. Hit: 1d6 +1 piercing damage, and the target is Grappled. The monodrone cannot use this attack again while it has someone Grappled. Once per turn, the monodrone can either move towards a target is has Grappled, or try to pull the Grappled target towards itself, up to 30 feet. This movement doesn't count as part of the monodrone's normal movement. If it is trying to move its Grappled target, and that target wants to resist moving, it must succeed on a DC 13 Strength saving throw to hold its position.

Mark Target. Ranged Weapon Attack: +3 to hit, 60/240, one target. Hit:  The target is invisibly marked with a distinctive heat signature. Until the end of the monodrone's next turn, Modron have advantage on Perception checks made to find the target, and any attack against the target has advantage if the attacker can see it.

Early Warning System. The moment the monodrone detects danger, it can send out a loud alarm audible to all creatures within about a mile, and/or a telepathic notice to its commanding duodrone if the duodrone is within 1,000 feet.

Emergency Data Transfer. If the Modron is destroyed by a target it can see, it can transmit all of its knowledge to another Modron within 120 feet just before being destroyed.