Diablo IV

Bartuc, Lord of Chaos boss fight guide for Diablo 4. Infernal Hordes alternate boss, Chaos Portal mechanics, 666 Burning Aether summon, Footfalls of the Waning World drop.

Special Activity Boss Lord of Hatred 12 min read

Bartuc, Lord of Chaos — Boss Guide

By the DiabloBytes team · Updated May 2026

Bartuc, Lord of Chaos is a special-activity boss accessed through Infernal Hordes — he sits outside the standard Lair Boss ladder rather than as another Exalted-tier rung. Burn 666 Burning Aether at the post-final-wave Spoils of Hell screen to skip the Fell Council and fight Bartuc directly. The arena uses a four-portal teleport system to dodge his rotating fire beams, sweeping lightning, and the intermission blood barrier. The headline drop is Footfalls of the Waning World — Bartuc is the listed primary target-farm source for the Dread Claws Warlock boots.

⚡ TL;DR

Tier: Special-activity boss (outside the Lair Boss ladder).
Summon: 666 Burning Aether at the Infernal Hordes Spoils of Hell screen.
Mat source: Infernal Hordes runs (Aether earned per wave).
Portals: 4 paired Chaos Portals — teleport across the arena. Mandatory for beam dodges.
Resistances: Cap Fire, Lightning, AND Poison. All three see heavy damage.
Reward: Footfalls of the Waning World (Dread Claws Warlock boots) + the in-mode Chaos Armor pieces.

Fight Mechanics

Phase	Mechanic	How to Handle
Throughout	Chaos Portals	Four purple portals spawn at the cardinal points of the arena. Each portal is paired with the one across from it — stepping in teleports you to its opposite. The fight assumes you use them. Beams, walls, and intermission barriers cut the floor into sections you can only cross via portal.
Throughout	Resistance check	Bartuc deals heavy Fire, Lightning, and Poison damage in roughly equal shares. Cap all three resistances before pulling. A single uncapped resistance is the most common cause of one-shots in this fight.
Throughout	Stagger bar	Standard Lair Boss stagger bar. Crowd-control and DoT effects build it. Stagger landing during a Phase 1 burst window deletes a chunk of his HP and skips part of the invulnerability rotation.
Phase 1	Tracking fireballs	Slow-moving fireballs lock onto your position and chase. Kite them in a wide arc — do not back yourself into a corner. They detonate on contact or after a few seconds; lead them away from your DPS spot before they pop.
Phase 1	Rotating fire beams	Bartuc emits two clockwise-rotating fire beams from his body. Stand in the gap between beams and rotate with him. If you get boxed in, dive through a portal to teleport out.
Phase 1	Lightning sweep beams	Two lightning beams spawn at opposite edges and sweep inward toward the center. The safe zone is the perpendicular axis — or jump through a portal to skip the sweep entirely.
Intermission	Blood barrier + invulnerability	Bartuc periodically becomes invulnerable and a solid blood-energy beam splits the arena in half. The only way across is through a Chaos Portal. Adds spawn during this window — clear them while waiting for the invulnerability to drop. High burst can skip the invulnerability phase entirely if you stagger him in time.
Phase 2	Circling poison waves	Six dark waves circle the arena in alternating directions. Watch the rotation pattern and weave between them — moving with the closer wave's direction is safer than against it.
Phase 2	Chaos orb crossfire	Chaos orbs open on opposite sides of the arena and launch shadow projectiles at each other. The flight path is a moving wall — keep moving along the line, not perpendicular to it.
Phase 2	Add waves	Vizjerei sorcerer adds and demonic minions spawn during transitions. Cleave them passively while keeping boss damage up. Do not stop attacking the boss to chase adds — they expire on their own if you maintain DPS.

Drop Table

Footfalls of the Waning World (Warlock Unique Boots) Best-in-slot for Dread Claws Warlock. Per current target-farm guides Bartuc is the listed primary source, with Astaroth as a secondary fallback.
Class Unique pool (Warlock-leaning) Bartuc's table tilts Warlock — the rest of the in-mode rewards include the standard Infernal Hordes pool plus Bartuc-specific class items.
Mythic Unique pool Bartuc rolls on the universal Mythic Unique pool. Resplendent Sparks salvage from unwanted Mythics fund targeted Mythic crafts at the Jeweler.
Resplendent Spark (Tormented) Tormented Bartuc kill grants 1 Resplendent Spark. 2 Sparks = 1 targeted Mythic craft after the LoH update.

Best Builds for Bartuc

Dread Claws Warlock

Direct beneficiary — Footfalls of the Waning World (BiS boots) is the marquee target-farm here. Run Tormented Bartuc the moment you have Aether to spare. Frequent teleports / Nether Step synergize with the portal mechanic for free damage uptime.

Whirlwind Barbarian

Tankiest pick for the cone and beam phases. Iron Skin + shouts cover the resistance burn. Walking Arsenal weapon-swap rotation handles the intermission-add waves cleanly.

Ball Lightning Sorcerer

Top single-target burst can outrace the invulnerability phase entirely. Stagger Bartuc fast, drop a Ball Lightning carpet through a portal, and skip a transition.

Penetrating Shot Rogue

Range-keep through the rotating fire beams. Cold Imbuement on add waves. Mobility-friendly for the Chaos Portal hops between phases.

Frequently Asked Questions

How do I unlock the Bartuc fight?

Bartuc spawns from the end-of-run reward selection in Infernal Hordes. After clearing the final wave, the Spoils of Hell screen offers a choice between The Fell Council and Bartuc, Lord of Chaos. Selecting Bartuc consumes 666 Burning Aether and ports your group into the boss arena.

Where does Burning Aether come from?

Burning Aether is the in-mode currency for Infernal Hordes. You gain Aether from killing demons during waves — dense pulls and elites pay out heavily. Higher-tier runs yield more Aether per wave; a single completed run typically supplies enough for a Bartuc summon plus a partial Spoils of Hell pull.

How do I get a Compass to enter Infernal Hordes?

Compasses drop from Helltide chests, World Bosses, and Whisper caches. You need a Compass to start an Infernal Hordes run, after which Bartuc is the post-final-wave alternate boss option.

How do the Chaos Portals work?

Four purple portals spawn at fixed positions in the arena. Each portal is paired with the portal directly across the arena — stepping into one teleports you to its opposite. The portals are a core fight mechanic: rotating fire beams, sweeping lightning beams, and the intermission blood barrier all assume you use them. Practice mapping which portal pairs with which during the opening seconds.

Can I skip the invulnerability phase?

In some builds of the fight, high-burst setups can stagger Bartuc and burst through the threshold before the intermission plays out fully. Behavior has shifted across patches — check the live patch notes if exact timing matters to you. Lower-DPS builds will see the invulnerability and the blood-barrier intermission play out completely; clear the adds during the wait.

How does Bartuc compare to Belial as a farm target?

Bartuc is the listed source for Footfalls of the Waning World, the Dread Claws Warlock BiS boots. Belial is the Pinnacle / Exalted Lair Boss reached via Betrayer's Husks and rolls on the universal Mythic pool with boosted Mythic chance. If you want Footfalls, run Bartuc. If you want pan-class Mythics, run Belial.

What is the difference between regular and Tormented Bartuc?

Tormented Bartuc costs 2x Aether plus 1 Stygian Stone. Higher HP and damage. Tormented kill drops 1 Resplendent Spark, guarantees a Greater Affix on at least one item, and unlocks the Mythic loot table needed for higher-weight rolls of Footfalls of the Waning World and other target items.