Chthonian
Chthonian — The Encounter
Burrowing horror that boils the earth from below · a boss your table can run with almost no prep. SRD 5.1-compatible.
Who Is Chthonian
Of the Chthonians the old grimoires speak in dread whispers, naming them children of a buried god who dwell leagues beneath the surface in tunnels older than mankind. They move through living rock as a man wades through shallow water, leaving no breach behind them, so that a hamlet may stand for generations atop a slumbering host and never know. When one rises it brings the heat of the deep earth with it; the ground steams, wells boil, and the dead are pulled down through the loosening soil. They are said to detest water above all things, for the flood drowns their fires, and the wise who would parley with them do so only on stone and never near the sea. They breed in vast subterranean clutches, and where the tremors of their passing are felt for many nights, a brood is surely waking, and the land above is already lost.
Run Chthonian in Sixty Seconds
- Hold the entrance. It hides underground with tremorsense 60 ft. and surfaces under the tightest cluster — don't let the party bunch up before it appears.
- Open with grapples. Bite the tank, then Tentacle-grab two backliners (escape DC 15) and reel them into the 5-ft. fire aura where every hit they land burns them back.
- Kill-priority is the grappled caster. A held spellcaster can't move out of the heat — the party must break the grapple or burn the tentacle (it grapples only two at a time).
- When bloodied, it dives. Use Sink on the next melee hit to vanish underground, then Earth Glide to a new spot — reset the fight and force the party to re-find it with no tunnel left behind.
- Three ways to run it: lone ambush that surfaces, drags, and sinks; the burrower that opens tunnels for a swarm of lesser spawn; or the slow siege-horror beneath a doomed village. Water and open stone are its weaknesses — smart players will exploit both.
Chthonian
Huge aberration, neutral evil
CR 6 · 2,300 XP · GUIDELINEBurning Touch. The chthonian's body radiates a smoldering subterranean heat. A creature that touches it or hits it with a melee attack while within 5 ft. of it takes 4 (1d8) fire damage.
Earth Glide. The chthonian can burrow through nonmagical, unworked earth and stone without disturbing it. While doing so, it doesn't displace the material it moves through.
Actions
Multiattack. The chthonian makes one Bite attack and two Tentacle attacks.
Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 17 (3d8+4) piercing damage plus 7 (2d6) fire damage.
Tentacle. Melee Weapon Attack: +7 to hit, reach 15 ft., one target. Hit: 11 (2d6+4) bludgeoning damage, and the target is grappled (escape DC 15). The chthonian has two tentacles, each of which can grapple one target.
Bonus Actions & Reactions
Sink (Reaction). When the chthonian is hit by a melee attack while above ground, it can burrow up to 10 ft. straight down, sinking into the earth. This movement doesn't provoke opportunity attacks.
A mountain of segmented, fire-veined flesh erupts from the broken ground, its tentacled maw steaming, the soil around it cracked and glowing like a dying ember.
Chthonian, Bound
Companion · acts on your initiative
Bound · GUIDELINETunneler (signature). The spawn can burrow 30 ft. through earth and stone, leaving a passable 5-ft. tunnel. Allies that follow within 1 minute move through it at full speed.
Actions
Searing Tentacle. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 9 (2d4+4) bludgeoning damage plus 3 (1d6) fire damage.
Reactions
Shield the Brood. When an adjacent ally takes fire damage, the spawn absorbs it, taking the damage itself instead.
A half-grown chthonian, scarcely larger than a plow-horse, that worms ahead to open the road and shrugs off the heat that withers softer kin.
Guideline numbers — formula-tuned and read from the miniature's design, not yet table-proven. Tell us how it ran in the comments.
How It Fights — by Tier
Same creature, scaled threat. The traits never change; only the numbers move.
Open by surfacing under the most clustered PCs so the tentacles can grab two at once. Kill-priority is the spellcaster the tentacles can drag prone and isolate. Pair it with a flagship horror or a brood of swarmers; it is a terror as a lone surprise but is not the centerpiece.
Open with a Bite on the front-line tank, then Tentacle-grapple two backliners and pull them into the burning aura. If clustered, surface in the middle of the party so Burning Touch punishes every melee swing. When hurt, use Sink to dive underground and re-emerge somewhere new — kill-priority is the grappled caster. Best fielded with minions or a larger lair-boss.
Run it as a tunneling siege monster amid a brood: surface, grab and burn, then Sink and relocate to scatter the party. Kill-priority is whoever can hit it underground or counter its grapples. Do not run it solo — pair it with a bigger threat or a swarm of lesser spawn so the action economy holds up against an 11th-level party.
Put Chthonian on the table
Download the presupported STL and run the fight tonight — the model, and the encounter that comes with it.
Get the STL on MyMiniFactory →Clay Cyanide Companion Rules v1
How a bound creature acts
- A companion acts on its owner's initiative, immediately after the owner.
- It uses the Companion block above — roughly ×0.6 HP and damage, no recharge abilities, and at most one reaction trait.
- It moves freely; it takes its Action only while its owner is conscious.
- At 0 HP a companion is broken, not dead — restored on a long rest unless your table rules otherwise.
Original Clay Cyanide material © Clay Cyanide LLC — explicitly not the non-SRD official sidekick rules.
Questions, Asked at the Table
What CR is Chthonian?
Its home tier is CR 6 (XP 2,300) for levels 5-10. Scale it down to roughly CR 2 for a tier-1 party (levels 1-4) or up to about CR 11 for tier-3 (levels 11-15) using the per-tier numbers above — traits and actions stay identical, only AC, HP, to-hit, save DC, and damage shift.
Can Chthonian be a companion or ally?
Not the adult itself, but a Lesser Spawn, Bound can serve as a companion (AC 14, 82 HP). It tunnels a passable road for the party, strikes with a searing tentacle, and throws itself in front of allies to soak fire damage — a living siege-engine bound to the party's service.
How do I make the fight tougher without raising the tier?
Add two or three Lesser Spawn as the brood, fight it on dry stone far from water so its fires never gutter, and let it use Sink aggressively to relocate. Conversely, give the party access to water, a flooded chamber, or open quarried stone (no Earth Glide) to ease the encounter.
Tell Us How It Ran
This work includes material taken from the System Reference Document 5.1 ("SRD 5.1") by Wizards of the Coast LLC and available at dnd.wizards.com/resources/systems-reference-document. The SRD 5.1 is licensed under the Creative Commons Attribution 4.0 International License available at creativecommons.org/licenses/by/4.0/legalcode.
Clay Cyanide Miniatures is not affiliated with, endorsed, sponsored, or specifically approved by Wizards of the Coast LLC. This content is compatible with the fifth edition of the world's most popular fantasy roleplaying game. Companion rules, lore, names, and original mechanics © Clay Cyanide LLC.
Technical Specifications
32mm, 75mm
STL, Pre-supported STL
Standard or ABS-like resin, 0.05mm layer height
Yes — ready to print, optimized supports included
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