Umbral Monument Stage 3 Guide: How to Beat the Ritual Vortex Boss in Arknights: Endfield

The boss doesn’t have an exploitable elemental weakness. What actually matters here is Stagger — how fast you can knock enemies down and land Finishers on them.

The Pyromancer’s fight runs on one core loop: it periodically summons clones and starts channeling its ultimate. If that channel completes, it hits your whole team with damage heavy enough to end most runs on the spot.

• The only way to stop the ultimate is killing every clone before the channel finishes.
• Clones go down fast once staggered, but they don’t stagger on their own — you need to apply Physical or elemental statuses consistently.
• Landing a Finisher on a clone does bonus damage and slashes the time it takes to break the next one.
• In Agony mode, you lose access to tacticals and recovery items entirely, so your team needs to sustain itself through skills alone.

The fight isn’t really about raw DPS on the boss. It’s about how fast your team can clear a clone wave under a timer within a timer.

A few comps handle the clone phase reliably. All of them lean on either high natural Stagger or grouping tools that let you hit multiple clones at once.

• Mono Physical — Mi Fu, a Vanguard-type Physical applier, Chen Qianyu, and Ember. Physical status stacks fast across this comp, and it pairs naturally with the Swordmancer Set for quick Stagger gauge fills. This is the comp day-one clears leaned on most.
• Zhuang Fangyi Electric — Perlica, Zhuang Fangyi, Arclight, and Gilberta. Electric applies control on top of damage, which buys you a few extra seconds during the clone spawn window.
• Rossi Hybrid — Mi Fu, Rossi, Perlica, and Gilberta. More flexible than Mono Physical if your roster is thinner on Physical units, at the cost of slightly slower Stagger.
• Laevatain Heat — Laevatain, Camille, Wulfgard, and Ardelia. Free-to-play friendly since none of these are limited units. Ember can tank the boss’s ultimate directly if your clone-clear timing slips.

Whichever comp you run, bring at least one unit who can group enemies. Clones spawn spread out, and chasing them one by one is how the channel finishes before you’re done.

1. Open on the Pyromancer directly. Don’t hold back Combo Skills — you want SP built up before the first clone wave hits.
2. The moment clones spawn, switch your focus entirely to them. The boss stops mattering until the wave is cleared.
3. Stack status effects across the clone group fast. Battle Skills, Ultimates, and Final Strikes all contribute to Stagger — use them together rather than saving them.
4. Land Finishers as soon as a clone staggers. Don’t wait to line up a “cleaner” kill — a delayed Finisher costs you the time you don’t have.
5. If you’re mid-ultimate on a unit like Laevatain, switch operators to land a Finisher rather than canceling the ult state. You can come back to it.
6. Once the wave is down, go straight back to the boss and repeat. The loop resets, and your window shrinks slightly each time.

Positioning matters more than it looks. Standing where you can hit two clones with one AoE skill saves seconds you don’t get back.

Agony removes your safety net, so your comp needs to survive on skills alone. Bring at least one dedicated healer instead of relying on items to patch mistakes. Ember and Ardelia both work well here since their kits sustain the team without eating into your damage rotation.

Finisher timing gets less forgiving too. At level 90, clones hit harder before they stagger, so a missed Finisher window costs more HP than it does on Normal. Run the fight once on Normal first if you haven’t already — it’s the cheapest way to learn the clone spawn pattern before the stakes go up.