D&D Homebrew Monster of the Week: The Air Control Unit

“Neat lookin’ statue! You think it might be worth somethin’?”

“No idea. Hey! It’s movin’!”

“Oh relax would ya. It’s just a sphere with some fancy fences.”

“I guess you’re right. After all, what’s the worst it cou–”

– Final words of two thieves.

Air Control Unit: The Overview

Coming in as the first creature from the Construct Compendium, the Air Control Unit (or ACU for short) is a low-mid level enemy clocking in at CR 6 and is designed to be a defender rather than an aggressor. Using the long fence-like structure around its body to both aid in deflecting attacks from its core as well as rapidly spinning to create powerful air currents, the ACU is a master of manipulating the air around itself to both shred opponents or send them flying with powerful gusts of wind. Despite it’s ornate design, the ACU can certainly take a hit, although it like most creatures prefers to keep distance and harass opposition from a distance with the fact it has that option to. Unlike most constructs, the ACU is quite intelligent and while will follow orders from its creator/master, it has the aptitude to adjust its fighting style if its opening round doesn’t meet expectations. Additionally, while unable to speak, it still can understand the Common language and be spoken to, leading to some instances being resolved diplomatically.

Stats and Abilities:

Agile, intelligent, and hearty to boot, the ACU is a creature with no one discernable weakness, making it a difficult encounter for even more experienced adventurers.

The two biggest weakness I gather from this statblock is that it struggles in close quarters fighting and doesn’t have a way to resist being shunted to a different plane of existence from the likes of the Banishment or Plane Shift spells (both requiring CHA saves). Relying on its high DEX and INT to evade and blast foes with spells, the ACU has no problems taking a hit from a stray attack or two, but will seek to reposition itself if cornered as while it can preform decently in a head-to-head fight for a bit, it will be outclassed by something designed and built to be a brute fighter.

• Stats and Skills: The ACU focuses on utilizing its ranged attacks and defending with its solid AC and Hit Point pool. Being able to quickly float about also aids them greatly as they can out pace most adventurers with relative ease. While not having any skill proficiencies, the ACU does get proficiency in STR and DEX saves, allowing it to resist attempts to grapple and restrain it as well as most offensive spells. Most other offensive spells that don'[t rely on a DEX save rely on a CON save instead, but often deal either Necrotic or Poison damage, and the latter being both more common and a damage type the ACU is immune to.
• Resistances, Immunities, and Senses: The ACU has a wide array of defenses, being outright immune to poison and resistant to lighting, thunder, and nonmagical weapon damage types. Thunder might be a bit of a stretch as thunder damage in D&D isn’t directly related to an instance of thunder, but more so anything relating to sonic waves. In a way it could be described as a more visceral from of bludgeoning damage as spells like Shatter violently destroy anything within the cube and deal double damage to objects or Constructs. Regardless, with the ACUs constructed design, lighting and wind themed capabilities, and being magical in nature, I’m content with the remaining immunities and resistances. Now, due to being a Construct and artificial in design, the ACU gets a good amount of conditions it’s immune to as well: Charmed, Exhaustion, Frightened, , Paralyzed, Petrified, and Poisoned. The former three are all due to the ACU’s decent mental scores and the latter three are due to being a construct as most Construct type creatures are immune to these conditions. One final one that should be added is the Prone condition as most creatures that hover in the air are immune to being knocked prone. Finally, unlike most faceless creatures that have blindsight, the ACU has darkvision. I always imagined the ACU had a little eye at the “front” of the fence structure around itself that it could see through. This means while most constructs don’t care whether its night or day, the ACU does its best work in the night or in dark areas, making it ideal to counter would be thieves who also prefer to skulk in the shadows.

Passive Abilities and Actions:

A staple ability that is in every construct as far as I can remember. More flavor than actual combat utility, but hey if a party escapes and needs to stop and lick their wounds, a construct won’t care too much and will press on while the heroes rest unless it is heavily damaged and intelligent enough to no it doesn’t stand a hance, or if it is guarding a specific place.

On a failed concentration check, this ability ceases to function until the end of the ACU’s next turn.

This is one of the ACU’s staple features, a defensive aura that’s useful not only for itself but for any possible allies nearby. This could pair nicely if the ACU stays at a range and has fellow ranged combatants paired with it, but this could also be a double-edged sword. Imagine if the ACU does have a ranged combatant that has slipped out of the thick of the fray and is trying to take a shot a creature locked in melee combat with the ACU. Sadly it will be rolling any attack towards the creature next to the ACU at disadvantage because ALL ranged attacks have disadvantage when targeting the ACU or anything within 15ft. of it, not just enemies of the ACU. Thankfully players can brute force their way in and a melee bruiser like a Barbarian or Fighter can help nullify this ability for a round allowing a Ranger or Wizard (ranged spell attacks would also be effected by Eye of the Storm) to get some good hits in before the ability resets.

As mentioned in the beginning, I envisioned the ACU to be a guardian and focusing on defending an area rather than prowling the realms killing randomly. Additionally, various constructs (i.e. the Animated Armor) get this feature to blend in and help their usually clunky bodies get a free surprise round on inexperienced adventurers. The ACU can maximize this with a high INT stat, picking exactly when is the best opportunity to strike and not “intruders have reached X threshold, now attack.”

Another staple feature for Constructs around the globe! This feature prevents being Polymorphed into something weak and helpless and being tossed aside for an hour, allowing the ACU to continue following its directives.

• At will: dust devil, ray of frost (5th level), thunderwave
• 3/day each: ice storm, lightning bolt, thunder step
• 1/day each: storm sphere, invisibility

Just like Absolution in last weeks post the ACU has some spells hidden up its metaphorical sleeves. Unlike Absolution, the ACU instead is what is considered an innate spellcaster, meaning that instead of following the normal spellcaster rules of having spell slots that can be used to cast spells of the same level or boosting spells of a lower level (i.e. casting Fireball with a 4th level slot instead of a 3rd level slot to boost the damage), innate spellcasters have a specific spell list and can cast certain spells only a certain amount of times before needing to rest, typically having spells it cast At Will and without limit, spells it can cast 3 times per day, and spells it can cast only once per day.

At Will:
–Dust Devil– Concentration spell that summons a small cyclone within a 5ft. cube (1 space). Each creature that ends a turn within 5ft. of the cyclone has to make a STR save, taking damage and being shoved away from the dust devil. If this was it, Dust Devil would be an alright spell, but on follow up turns as a bonus action you can move the cyclone 30ft. in any direction as a bonus action and additionally, if the cyclone moves over loose debris (dirt, gravel, sand) it additionally creates a 10ft. radius of heavily obscuring dust centered on the cyclone. This is a great opening move that the ACU loses nothing by immediately firing off at the start of combat, and because it can cast this usually 2nd level spell at will, it has no issues dropping concentration whenever it sees fit.
–Ray of Frost– A cantrip that can always be casted however many times as the caster wants, no matter if they are an innate spellcaster or standard spell caster. Like many damaging cantrips, Ray of Frost is boosted as the caster gains levels and as the ACU is roughly on par with a 10th level spellcaster, it wouldn’t quite hit the threshold of the 11th level bump Ray of Frost would get so it remains a 2d8 damage cantrip, which isn’t too bad as a ranged option.
–Thunderwave– A decent “Get off me!” tool that creates a barrier of thunderous energy in a 15ft cube centered on the ACU. Everything inside has to make a CON save, taking 2d8 damage and being knocked back on a failed save. Requiring a CON save does little to help this spell and with such a short range and minimal damage, it really is only useful as a last ditch attempt to create space to get away.

3/Day:
–Ice Storm– A conjured storm of hail appears and fills a 20ft. radius, raining down in 40ft. column. Each creature in the area has to make a DEX save to avoid both 2d10 bludgeoning and 4d6 cold damage as hail rains down. Additionally until the end of the caster’s next turn, the area is considered difficult terrain due to a layer of ice that now covers the ground. Good offensive capabilities, great area control, good spell all around. No notes.
–Lightning Bolt– Ahh a classic. The often overlooked sibling of the infamous Fireball spell. Sharing Fireballs DEX save requirement and 8d6 of damage (lightning instead of fire now, surprise surprise), Lightning Bolt’s area of effect is now an 100ft. line instead of Fireball’s 20ft. radius. So it’s not as easy to clump together a group of adventurers to maximize usage, but with its high movement speed the ACU can quickly reposition to get a good angle.
–Thunder Step– The ACU’s big teleportation option, allowing the caster to quickly teleport up to 90ft. away. Additionally, each creature within 10ft. of the spot you left before teleporting has to make a CON save, taking 3d10 thunder damage on a failed save as a sonic boom erupts from the point. The ACU can also teleport one creature of it’s size (Large or smaller) for free as well. Decent damage though the CON save leaves a lot to be desired. Such is the way with most “thunder” themed spells, though its more of an escape tool rather than a damage dealer anyways.

1/Day:
–Storm Sphere– Another concentration spell, but this one is a much better offensive spell than Dust Devil. Covering a 20ft radius sphere that imposes difficult terrain and deals 2d6 bludgeoning damage to everything inside on a failed STR each turn. The real juice of this spell comes from the bonus action ability where you can target one creature within 60ft. of the center of the sphere and hit them with a stray lightning bolt, rolling a ranged weapon attack to hit them and dealing 4d6 lightning damage.
–Invisibility– The ACU’s ultimate “Get out of Jail Free,” card. Lasting for a full hour with the only caveat being it can’t cast spells, make attack rolls, or deal damage. Another concentration spell, but this is used solely if the ACU needs to bolt or if it feels like it can end the fight by just quickly repositioning and it doesn’t have Storm Spere up and is out of Thunder Step uses. All in all, a good solid spell list.

Alright so we got quite the beefy ability here so we are gonna break it down and talk about the two options respectively: Scatter and Shred.

A massive wall for any melee oriented character as closing the distance will first start with a decent STR save (will probably revised to an Athletics check instead) and forces you to move through difficult terrain the entire time. Now as a guardian, the ACU is not inclined to move from what its defending if it doesn’t have to and will initiate the fight with this ability unless it is already in the middle of the fray when it springs the ambush. Now we have talked about Difficult Terrain a lot, but what does that entail? The short of it: halved movement speed. For every 1ft. of movement you need to spend 2 instead, so to move 5ft. (from 1 tile to another) it costs 10ft. A massive radius of difficult terrain (which thankfully doesn’t stack with the ACU’s other spells which also cause difficult terrain) means its going to be a challenge to approach the thing, much less get close enough to hit it, and all the while the ACU can keep pace by shifting about with its quick movement speed, pelting those who approach it with Rays of Frost from a safe distance.

Creatures that fail the save by 5 or more are also blinded until they either leave the radius or until the end of their next turn (assuming they don’t fail the save again).

So what happens if the ACU kicks off combat with enemies already close by or if something does push through the gale force winds of Scatter? Well the winds intensify into a razor-sharp wall designed to shred whatever is nearby to ribbons. In hindsight, this ability can be tweaked as this does more damage than its standard attack action. A monster we can look to is the Gearkeeper Construct from Explorer’s Guide to Wildemount which has a similar feature. “Whirling Blades. Any creature that starts its turn within 5 feet of the gearkeeper takes 4 (1d8) slashing damage.” I think this is a bit more nicely flavored, but if the required DEX save were to stay, reducing the damage from 4d8 to say 2d10/2d12 would be fine. That gives it the oomph to be a worry for martial characters yet not penalizing enough to immediately shred through a frontliner’s hit points in a couple rounds. The ACU shifts into this form once it feels as though Scatter either isn’t useful against whatever is rushing it down, or once it feels like it can push the offensive against a creature, whittling down their hit points little by little.

One of the only two standard actions the ACU has in its kit, Gust Blade functions as the ACU’s one melee feature, allowing it to deal with attackers that are threatening it even after the effects of either Wind Manipulation option. While dealing a pretty solid chunk of damage, this is an all or nothing and the only attack it can make in a turn, so it’s not too problematic for the ACU to have this. this also pairs nicely with the bonus action capabilities from either Dust Devil or Storm Sphere

Depending on how combat starts with the ACU, it could immediately start off the ambush and firing this off if the intruders are nicely clumped together. A standard big damage recharging option. A rather staple ability and an option to quickly threaten everybody in the party if they place recklessly. The knockback also allows the ACU to help reset itself if if it is being threatened and doesn’t have any more uses of Thunder Step, though this would be a niche case as it would likely be better to simply switch to Scatter and try to escape that way.

Revisions:

All in all, I’m quite happy with this creature. The ACU is designed to be a low level mini boss of sorts, nothing too strong but definitely a step up from most creatures a party would have faced up until this point. Thanks to it’s defensive nature, the ACU shouldn’t pursue wounded parties unless said party is actively running away with what the ACU is protecting. Good defensive bulk with its hit points, AC and Wind Manipulation feature, great offensive capabilities between its spells, and lastly great movement and area denial leaves the ACU a near perfect all rounder monster. the only major adjustment i would make is changing Scatter from a STR save to an Athletics check, allowing for martials to close the distance slightly easier.

This might be my favorite monster up until this point, and words cannot express how happy I am with it. I love monsters that can function in every situation when compared to ones who do one thing the best, and the ACU is perfectly suited to be dropped anywhere. Need an ancient artifact protected? Depending on the level, drop a few of these down. Need a Person of Interest defended and watched, have one of these follow them about and idle in their garden.