‘Heart of the Iron God’ Part 4 – Adventure for 13th-Level Characters

This is the fourth part to my 5th edition conversion of the 3rd edition adventure, ‘Heart of the Iron God.’ It covers the final chambers of the Colossus, 25 – 27, the adventure conclusion, and the appendix.

If you haven’t already viewed the first part already, be sure to start there.

‘Heart of the Iron God’ Index

Colossus Chambers

Note that all descriptions assume the Colossus is facing south.

25. Bridge

This large hemispherical room is set into the lower half of the Colossus’s head. Banks of controls appear to allow manipulation and control of the Colossus, and you spot a periscope-like viewing device hanging from the ceiling. Several chairs surround one particularly luxurious thronelike seat in the center. Curved staircases line the edge of the chamber, going up and down to different levels. To the south is a wall of transparent crystal, and beyond that, you see a small featureless chamber of crimson steel.

The staircase heads down to area 19 and up into area 27. A successful DC 19 Intelligence check is required to understand the functions of the levers and buttons, which override any controls activated in a particular room. Area effect spells have a 50% chance of rendering one of the controls useless. The plane of crystal is difficult to break (AC 23, 120 hp) and separate this chamber from the mouth. The periscope allows the gnomes to view the battlefield in front of the Colossus when the mouth is closed. The controls perform as follows:

  • Gold lever. Opens/shuts the mouth.
  • Large black button. Raises/lowers screen.
  • Yellow lever. Deactivates/reactivates the levitation discs.
  • Pale blue lever. Deactivates/reactivates the force barriers in area 18.

Several plain levers control the basic limb movement of the Colossus. Several gauges show the engine and power status of the Colossus.


Glymm (see the appendix) sits in the captain’s chair (the thronelike chair in the middle of the room), giving instructions to three gnome engineers. He is here even in the event that the crew is aware of the characters’ presence. Glymm values his position as captain and views any intrusion as a threat. Khrull (see the appendix) stands nearby, sulking constantly over the gnome’s superior position of command (but recognizing that he doesn’t have the knowledge necessary to pilot the construct). Unless the PCs have incredible stealth, it is likely a large battle unfolds here, although the other gnomes flee from any combat.

Tactics. Glymm quickly vacates the pilot’s chair when the characters enter, moving back and casting haste, followed by alternating defensive and offensive spells. If the alarm has been sounded, he has already cast his long-duration defensive magic and is not surprised when the characters arrive. Khrull follows similar tactics, except for casting haste, using his offensive magic before resorting to melee attacks.

Combat in this chamber almost surely alerts Xentarich. He holds his position in the brain (area 27), but if the characters seem to be having an easy time of the battle with Glymm and Khrull, Xentarich can appear after a few rounds to even the score and provide an especially challenging encounter.

26. Mouth

This chamber is situated within the large jaw of the Colossus, and the walls, floor, and ceiling have been painted a dark crimson. A staff has been driven in the floor at its top, and the wall in front of you appears to be some kind of heavy gate that can be lowered and raised. A small red carpet adorns the floor beside the staff. A steel pole ascends through a hole in the ceiling of this chamber, and a steel lever is set in the wall nearby.

This small chamber is blocked off from the main bridge by a sheet of crystal. The staff is Xentarich’s addition to the Colossus and has been enchanted. When a creature speaks into the crystal, its voice can be heard for hundreds of feet in every direction. Presently, the mouth is closed. The pole leads up to area 27. If the staff is removed, its power fades instantly. The lever allows the mouth to be opened.


The small red carpet that adorns the floor of the mouth is, in fact, a 3-foot by 5-foot carpet of flying, as last resort for Xentarich if he must escape.

27. The Brain

This hemispherical chamber is composed of ornately crafted walls of curved metal. Two great windows of softly glowing red crystal overlook the land around the Colossus. A curved staircase leads down to the decks below, while a pole leads through a hole in the floor. A floating orb of rainbow-colored light hovers int eh center of this chamber, shedding a cascade of scintillating light across the room. You notice two curved bookshelves against the walls of this room and a luxurious bed.

The steps lead down to area 25, and the pole leads to area 26. The orb is the manifestation of the ancient priest’s spirit, and it can sense any living being within 40 feet; if it notices anyone enter, it warns Xentarich of possible foes.


Xentarich (see the appendix), the leader of the forces in the Colossus, almost never leaves this chamber, since he is in near constant negotiation with the spirit in the orb.

Tactics. If Xentarichs is aware that a fight is imminent (such as by sounds of battle emanating from the bridge) he magically prepares himself for combat with as many defensive spells as he has time to cast. Should a fight go badly, he tries to make for his carpet of flying (area 26) or teleports back to his secret base (see area 16) to lick his wounds. In combat, Xentarich doesn’t pull any punches; the Colossus is too good to give up easily. He uses forcecage immediately, trying to capture as many tough melee combatants in it as possible. He then focuses on other spellcasters. Xentarich tries to gauge the characters’ strengths by their appearance, casting spells like finger of death on those who look to have poor Constitution saving throws, and spells such as disintegration on those who look to have poor Dexterity saving throws.


A cupboard contains a small casket with 2,700 gp, and 10 small rubies (30 gp each).

One of these is shaped like a heart and is magically enchanted. This is the magic key to open area 23.

Xentarich’s collection of books is quite valuable (2,000 gp). The shelves also hold his spellbooks. One is a Boccob’s blessed book (see the appendix) which contains all his 3rd through 7th-level spells. The second book contains all his 1st and 2nd level spells.

Spellbooks. Xentarich’s two spellbooks are stored in area 27 and contain all the spells listed on his stat block, as well as the following: 1st–charm person, disguise self, feather fall, grease, sleep, true strike, unseen servant; 2nd–alter self, arcane lock, darkness, detect thoughts, enlarge/reduce, knock, fear, see invisibility, suggestion; 3rd–fly, glyph of warding, major image, protection from energy, tongues, vampiric touch; 4th–polymorph; 5th–Bigby’s hand, cloudkill, dominate person, passwall;  6th–legend lore, magic jar; 7th–sequester.


If Xentarich is defeated, read the following:

The mage gasps a last short scream before collapsing to the floor. AS the life in his eyes fades, the glowing orb begins to flicker nervously. It changes color to a pale blue and you hear a voice within your minds. “Who are you? Vile creatures of evil, what have you done to Xentarich?” The orb begins to glow a deep red.

The characters must now convince the mind they mean no harm. A successful DC 19 Charisma (Persuasion) check convinces the spirit that the characters are acting for the greater good, but another DC 27 Charisma (Persuasion) check is required to convince the spirit that Xentarichs was tricking it. If the characters show some sort of proof (perhaps by bringing one of the gnome engineers here and showing the spirit Khrull’s holy symbol), they can receive advantage on this check. Being gentle-but-firm is the best approach here. A good cleric or paladin can convince the spirit of their alliance to the good gods, also offering advantage on the Persuasion checks.

If the characters are determined to persuade the spirit of their intentions and do not give up, or they make the successful checks above, read the following:

“Oh, merciful Gods how I have been tricked! The blood of innocents has been spilled through my carelessness. I thank you, heroes, for freeing me from the trickery, but I feel the years have withered my soul and twisted my reasoning. I beg of you a boon–now that you have slain those that used me, will you grant me freedom? I have been trapped here longer than I can remember and I desire to continue my journey into the afterlife, something Xentarich denied me. I can no longer stand to exist in the construct; please set me free.”

Once it is convinced of the characters intentions, the spirit grows very depressed and horrified at the carnage the Colossus has wrought, and the construct grinds to a halt. It readily answers any of the characters questions, although its voice grows more distant and the answers curter as the conversation wears on. If the characters fail to persuade the spirit, act hostile, or otherwise make a mess of things, the spirit bellows something about “the forces of evil will never control the Heironean Colossus” and activates its self-destruct sequence (see below).

If the characters agree, the spirit tells them of the heart chamber, informs them of the key in the cabinet, and instructs them to destroy the heart of the Colossus to release its spirit. The spirit recommends the characters set up a quick escape route to flee from the Colossus once the heart is significantly damaged. It informs them that they’ll have roughly 30 seconds to get clear from the construct before it is destroyed. If they refuse or take too much time to make a decision, the spirit becomes anxious and the Colossus begins to pace anxiously. The spirit cannot be convinced by any means that anything other than its destruction is safe for the world and if the characters hem and haw too long, it informs them in a near-hysterical tone that it is activating the Colossus’ self-destruct sequence.


In this case, the orb glows a bright red and high-pitched beeping begins to fill the entire construct. It grows more frenzied as the countdown continues, and the construct begins to shake and groan. The characters have 1 minute to escape the Colossus, after which time the construct explodes destroying the Colossus. Each creature within 100 feet of the Colossus must make a DC 20 Dexterity saving throw. On a failed saving throw, a creature takes 20d6 fire damage plus 20d6 thunder damage if it is within the Colossus, or 10d6 fire damage plus 10d6 piercing damage if it is outside of the Colossus. On a successful saving throw, a creature takes half damage.

There is only one way to keep the Colossus intact. A wish or miracle spell frees the soul from the energy sphere without any destruction but creates a complete power failure. To restore the Colossus, a new and willing recipient must allow a powerful spellcaster to cast a trap the soul spell, imprisoning him or her within the sphere to power the Colossus.

Once the Colossus is destroyed the lords of the lands terrorized by the construct host a huge celebration. The amazing accomplishment by the heroes draws a significant amount of attention to them, and they find their prestige almost legendary in the immediate area. Nobles and rich merchants from threatened lands nearby scrape together a chest of 8,000 gp that they aware the PCs.

If the spirit was freed and the Colossus is intact but immobile, the nobles that own the land claim ownership of the fallen giant and hire a team of wizards and investigators to investigate the machine. The characters might contest these claims, causing some tension between the group and the local nobles. Alternatively, the church of Heironeous might claim the Colossus as their property, further complicated the issue of ownership. If the characters still have the maps from area 4, the rulers of the land might wish to investigate the original homeland of Xentarich and could consider hiring the characters as envoys. Characters who have visited the underground cavern lair of Xentarich might wish to teleport back to explore the area, and possibly the strange lands beyond. In several years time, a new Colossus could be built, and what better officers to crew the construct than the characters who defeated the original? The Colossus might be sent wading through the ocean in search of strange lands to investigate or conquer.

In the even tthe Colossus is destroyed, another might show up later with a new crew, built from plains Xentarich recorded in his lair. This group might be composed exclusively of Erythnulites, or perhaps the new Colossus has even deadlier weapons and abilities at its disposal.


What follows are the new monster and magic item additions necessary for this adventure.

Dramatis Personae

The Colossus is lead by four NPCs of note.

Glymm is the leader of the gnome technicians and the chief pilot of the Colossus.

Khrull is an agent sent by the church of Erythnul to ensure that Xentarich does not stray from his mission of destruction.

Torax a fearsome minotaur barbarian, maintains order among the troops of the Colossus.

Xentarich is the mastermind who discovered the Colossus and got it running again. He is a powerful wizard who craves power above all else.

The Crew of the Colossus

Xentarich has hired a small army with his funds. Due to his own personal wealth, he has very experienced combat veterans at his disposal.

Darkblades. The melee fighting forces of the Colossus, Darkblades act as guards and man the ballistas in the hands.

Nighthawks. The Nighthawks are deadly trained archers. They can be seen flying around the Colossus in gliders, firing on innocents below the machine.

Storm Hammers. The four bugbears known as the Storm Hammers act as the shock troopers for the Colossus.

New Monsters

Two new monsters appear in the adventure ‘Heart of the Iron God.’

Chaos beasts are horrific, amorphous monsters that can turn a creature into mush with only a touch.

Advanced will-o’-wisps are powerful spirits that resemble orbs of glowing light.

New Magic Items

There are a few new magic items located throughout the Colossus.

Boccob’s blessed book is a magical tome that makes it easy for a wizard to store and record spells.

Robe of powerlessness is a cursed item that drains its wearer of its Strength and Intelligence.


‘Heart of the Iron God’ Index


Thanks for reading!

This was a fun project and actually the first time that I’ve converted a full Third Edition adventure to Fifth Edition. At roughly 15,000 words, it was quite the undertaking, too.

This entire project was requested by a Patron. I, admittedly, went a little overboard. They’d only asked for a “Talos-like” kaiju. What should have been 5,000 words became so much more.

If you’d like to put in a request, too, be sure to check out my Patreon. It’s only $3 to join and you get PDFs of all my good stuff.

Check out DMDave’s Patreon.

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