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

Disintegration. If the pentadrone dies, its body disintegrates into dust, leaving behind anything it was carrying.

Multi-Spectrum Sensors (1000 ft.). The pentadrone 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 pentadrone can see heat and other forms of radiation outside of a humanoid's visible spectrum. The pentadrone can also "see" sound waves and vibrations. The pentadrone 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 1,000 ft., the pentadrone can see as well as an average humanoid.

Magic Resistance. The pentadrone 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.

Telepathic Network. The pentadrone serves a hub telepathically linking any Modron within 1,000 ft. All Modron within the pentadrone's network (including the pentadrone) know each other's location and condition, can share each other's senses, and can communicate telepathically.

Innate Spellcasting (Psionics). The pentadrone's innate spellcasting ability is Intelligence (spell save DC 16). The pentadrone can innately cast the following druid spells, requiring no components.
1/day: Teleport, Plane Shift

Teleportation Beacon. The pentadrone functions as a permanent teleportation circle. Its sigil sequence shifts regularly in a complex mathematical pattern meant to be accessible only to Modron. If a non-Modron creature attempts to teleport to the pentadrone's coordinates, in addition to learning its sigil sequence, a non-Modron creature must succeed on a DC 18 Intelligence saving throw while teleporting in order to count the teleportation circle as a familiar location.

 Refueling Station. Pentadrone can produce an artificial replication of the high-energy psychomorphic gel that is the Modron's favored fuel source. All Modron must consume a portion of this gel at least once a week to continue functioning.

Freedom of Movement. The pentadrone ignores Difficult Terrain, and magical Effects can't reduce its speed or cause it to be Restrained. It can spend 5 feet of Movement to escape from nonmagical restraints or being Grappled.

Siege Monster. The pentadrone deals double damage to Objects and structures.

Multiattack. The pentadrone can make up to five attacks with its tentacle-like rays, each of which it can replace with one use of Fling or Vitrifying Spray.

Rays. Weapon Attack: +9 to hit, reach 30 ft., 1 target. Hit:  (3d6+5) bludgeoning damage. On a hit, a target that is Large or smaller must make a DC 16 Strength saving throw or be Grappled. As long as it is Grappled, it is Restrained. As an Action, the Grappled creature may repeat the saving throw to escape. The pentadrone has five rays which can be used to attack or hold Grappled creatures.

Fling. One object held or creature grappled by the pentadrone is thrown up to 60 feet in a direction of the pentadrone's choice and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 16 Dexterity saving throw or take the same damage and be knocked prone.

Vitrifying Spray (Recharge 5-6). Starting from a point within 20 feet of the pentadrone, one of the pentadrone's arms releases a 10 foot cone of vitrifying gas. Any creature caught in this cone of gas must make a DC 14 Constitution saving throw or be Vitrified (Petrified, with a vulnerability to bludgeoning and force damage.) A Vitrified creature shatters if its hit points drop to 0. A creature that is Vitrified while mid-air falls 500 feet on each of its turns. A Vitrified creature may repeat the saving throw to reverse its Vitrification at the end of each of its turns. The pentadrone is immune to its own vitrifying gas.

Factory Mode. The pentadrone begins producing a Swarm of Xenobots or a Torpedo Slug (Cryogenic, Incendiary, Concussive, or Poison). The pentadrone can take no other Actions until it produces the creature at the end of the pentadrone's next turn. The produced creatures drops up to 500 feet when it emerges, and may act immediately after being produced, sharing Initiative with the pentadrone and taking its turn immediately after the pentadrone's turn. The pentadrone controls creatures produced in its factory directly while they are within its telepathic network (1,000 ft.), and can give them instructions to obey while outside of that range. If a produced creature has no active instructions it can follow, it will attempt to return to the pentadrone. The produced creatures will disintegrate after 1 minute (ten turns). 

Graviton Beam. A 10 ft. radius cylinder centered under the pentadrone and extending down to the surface is crushed with tremendous pressure until the end of the pentadrone's next turn. On that turn, the pendadrone may decide whether to extend the duration of this effect or not. Any creature in this area must succeed on a DC 18 Strength saving throw or take 8d8 force damage and fall Prone. On a success, a creature takes 4d8 force damage and does not fall Prone. Any creature that enters the cylinder or starts its turn within the cylinder while this ability is active must make the same saving throw. Everything within the cylinder is difficult terrain. The land under the cylinder is also compressed, forming a 5 ft. deep pit. The walls of the pit are smooth and compressed, making them difficult to climb. If the terrain is something that is easily compressed or pushed away, such as mud, snow, sand, etc., 10 ft. of that terrain is compressed or pushed away until harder terrain is reached. Attack rolls against something within this cylinder that originate outside this cylinder have disadvantage. The pentadrone cannot move or take any Actions while this ability is active.

Antigraviton Beam. A 10 ft. radius cylinder centered under the pentadrone and extending down to the surface is lifted towards the pentadrone until the end of its next turn. On that turn, the pendadrone may decide whether to extend the duration of this effect or not. Any loose objects and Large or smaller creatures within this area are lifted towards the pentadrone 60 ft. on each of the pentadrone's turns, and remain suspended in the air for the duration. A creature in this area without the ability to fly can move only by pushing or pulling against a fixed object or surface within reach, which allows it to move as if it were climbing. Moving away from the pentadrone while in this cylinder is treated as moving through difficult terrain. Attack rolls against something within this cylinder that originate outside this cylinder have disadvantage. The pentadrone cannot move or take any Actions while this ability is active.

Cargo Hold. While adjacent to the pentadrone, a willing creature, a creature Grappled by the pentadrone, or a creature caught in the pentadrone's Tractor Beam can be enclosed in the Cargo Hold inside the pentadrone. By using this Action, the pentadrone can add or expel any number of creatures or objects to the Cargo Hold during this turn. The Cargo Hold can contain any number of creatures and objects that can fit within a space equal to a cube with 10 ft. sides (8 Medium creatures). A creature within the Cargo Hold can target the pentadrone or any other creature within the Cargo Hold with any of its abilities. The pentadrone chooses whether a creature within the Cargo Hold is Blinded, Deafened, and/or Restrained at any time. A creature within the Cargo Hold has total cover from any attacks and other effects from outside the Cargo Hold.  If the pentadrone takes 30 damage or more on a single turn from creatures inside it, the pentadrone must succeed on a DC 20 Constitution saving throw at the end of that turn or expel everything contained within the Cargo Hold, all of which exits in a space within 10 feet of the pentadrone. If the pentadrone disintegrates, creatures and objects within the Cargo Hold take 8d6 fire damage and are freed.

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 1,000 feet just before being destroyed. If it chooses a Modron of lower rank,  It can also give a final simple order to that Modron, which the Modron will attempt to fulfill before doing anything else, including beginning a promotion upgrade. If it chooses Modron of one rank lower, it can select that Modron as the one who will be promoted to fill its rank, even if it isn't the closest. 

The pentadrone can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. The pentadrone regains spent legendary actions at the start of its turn.

Scan. The pentadrone makes a Wisdom (Perception) check.
Ray Swipe. The pentadrone makes one attack with a Ray.
Cargo Hold. The pentadrone adds or expels any number of creatures or objects from its Cargo Hold.