Control Resonant: The Physicist Boss Guide

TL;DR

The Physicist is the Underpass Resonant, found at The Spire after completing Recursions and Iterations.
You need Shift and three Astral Keys to reach the boss arena.
The fight has multiple phases — arena changes, debris volleys, ground sweeps, and summoned minions.
Never get greedy. Attack in short bursts and reposition constantly.
After the fight, choose between Spike or Astral Rebuke — both apply Astralized.
Rewards also include the Untapped Golden Earrings artifact, a Reset Item, and 3,000 Source.

Table of Contents

Who Is The Physicist in Control Resonant?

The Physicist is one of the six named Resonant bosses in Control Resonant. It is the boss tied to the Underpass zone. The quest log calls the mission The Underpass Resonant, but the creature Dylan actually fights is called The Physicist.

It appears as a massive spiked disc entity floating in the Astral Plane. It is fast, it punishes players who stand still, and it changes the battlefield under your feet. This is not a boss you can out-muscle. You need to move smart and hit when the window opens.

Want to see where The Physicist ranks among all enemies? Check our full Control Resonant all bosses and where to find them guide.

When Can You Fight The Physicist?

The Underpass zone does not open until you complete the main quest Recursions and Iterations. You cannot access The Spire or start this boss fight before that point.

You also need the Shift (Gravity Shift) ability to climb The Spire. Make sure you have it before you head there.

Need help getting to that point first? See our Recursions and Iterations walkthrough.

Where to Find The Physicist – Location Guide

Control Resonant Boss 5 The Physicist Location

Head to The Spire in the Underpass zone. It is a tall, glowing Astral structure visible from the main path. Here is how to reach the boss:

Stand north of The Spire and look for the eye icon, or start climbing to trigger the Underpass Resonant quest.
Use Shift on the red blocks on the left side of the fast travel door and walk up the side of The Spire.
Defeat the enemies at the top until the red blockage clears and turns into bright white light.
Go through the opening to enter the Astral Plane.
From here you will find three locked doors. Each door needs its own Astral Key.

Also check our Control Resonant The Underpass Resonant walkthrough for the full step-by-step quest guide.

All 3 Astral Key Locations in The Underpass

This is where most players get stuck. The three Astral Keys are not sitting next to their doors. They are on side paths that branch away from the main route. Miss one and you cannot move forward.

Astral Key 1 – The Dining Room Key

From the first locked door, drop down to the floating platforms on the left. Follow the side path. It leads past a chest encounter and a wall-running section. The key is at the end of this branch. Grab it and return to use it on Door 1.

Astral Key 2 – The Bedroom Key

The second key requires Gravity Anomaly traversal. Follow the path across floating walls until Dylan ends up running upside down. The key sits inside a room styled like a bedroom, inside an iron cube at the end of the branch. Return and use it on Door 2.

Astral Key 3 – The Inverted Corridor Key

The third key is tied to a chest that changes position. Follow the side branch beyond Door 2 and track where the chest relocates. The key is found at a desk inside an inverted corridor at the end of this route. Use it on Door 3 and the arena path opens straight ahead.

After collecting all three, open each door in sequence and proceed forward to reach The Physicist.

How to Beat The Physicist – Full Boss Fight Guide

The Physicist fight has multiple phases. The arena changes shape across each one. The boss will punish you hard if you try to go for big combos without repositioning. Short attacks followed by movement is the correct approach throughout the entire fight.

Phase 1 – The Opening Chase

As soon as the fight starts, run. The Physicist chases Dylan and charges a large area explosion when it gets close. Do not try to attack immediately. Sprint away until it stops chasing and the explosion goes off. Once it settles on the ground, close in and get some hits in. Do not overstay. Pull back before it moves again.

Phase 2 – Debris Volleys and Ground Sweeps

The Physicist rises into the air and throws three waves of debris outward. The safest way to survive this is to sprint in a wide circle around the arena. Trying to judge each individual piece of debris is harder than just keeping your run going in a curve.

When it drops back to the ground, it performs a limb sweep at low height. The counter is simple: jump into the air and attack from above. Any time The Physicist comes near the ground, be aggressive. Use aerial combos if you have them. Minion abilities you have unlocked are useful here for applying chip damage when the boss darts out of reach.

The boss is also protected during its slam sequence. Do not waste your abilities trying to damage it at that point. Focus on staying alive and finding your footing as the arena shifts.

Phase 3 – Arena Transition and Split Form

Once you drain the first health section, The Physicist slams the ground and flies away. The platform you were standing on may be destroyed. Follow the newly opened path to reach a new circular arena further down The Abyss.

When you land, The Physicist will break apart into several smaller enemies. You need to kill all of them before the boss reforms. Do not ignore any of them. Once they are all dead, The Physicist comes back together in full and the fight continues.

Phase 4 – Ground Spikes and Minions

After rebuilding, The Physicist adds a new attack: it launches spikes from the ground at your location. Keep moving so the spikes cannot track you into a corner. There is still a damage window during this attack if you do not get greedy.

At roughly 50 percent health, the boss retreats again. Follow it to the next platform. This is the toughest phase. The Physicist stays on the battlefield but now summons two additional orb enemies at the same time. You must deal with both the boss and the minions together.

Kill the minions first. They add too much pressure if left alive. Once they are gone, return to the same rhythm of short attacks and movement against The Physicist.

Final Phase – Execution

Keep chipping away at The Physicist through its rebuilding and minion sequences. Once its health is fully depleted, you will get a prompt to Falter The Physicist. Hit the button when the prompt appears. Perform the execution jump into the center to finish the fight. After the entity is dormant, approach it and commune with it to calm the Resonant and end the encounter.

Physicist Boss Fight Tips

Never stop moving. The arena changes constantly. A fixed position will get you killed.
Dodge falling slabs. The boss drops large semi-spherical debris across the reflective platform. Keep moving so they never land on you.
Save some minion abilities for health recovery. You cannot use health items inside boss arenas.
Circle during debris volleys. Wide sprinting circles outrun the waves much more reliably than trying to dodge individual pieces.
Kill summoned minions immediately in the later phase before refocusing on The Physicist.
If your damage is very low, leave and come back. You can exit the Resonant route at any time. Spend Talent Points and improve your Aberrant before returning.

If you are struggling with your overall build, check our Control Resonant beginner tips and how to respec guide.

Spike vs Astral Rebuke – Which Ability Should You Choose?

After defeating The Physicist, you choose between two Combat Abilities. This is a permanent choice for this playthrough. Both abilities apply Astralized, which increases buildup of Burn and Infected on enemies.

Spike

Spike summons a spike that attacks or knocks down a targeted enemy. It does between 317 and 367 damage with a Falter value of 9 to 64. The key upside is that it works as autonomous pressure — the spike applies damage even when Dylan is focused elsewhere. It pairs well if your build already uses summoned allies or you want something attacking while you reposition.

Astral Rebuke

Astral Rebuke is a homing spike that erupts from beneath an enemy and launches them into the air. It does 459 damage and has a Falter value of 57. It needs a grounded target to work, but it is a direct, one-button disruptor. Launched enemies open them up for aerial follow-up attacks, which makes it the stronger choice for players who use melee and aerial combos.

Which One to Pick?

For a melee-focused or combo-heavy playstyle, Astral Rebuke is the cleaner pick. It immediately disrupts enemies and feeds into aerial attacks.

Choose Spike if your build is already summon-heavy or if you want hands-off pressure on enemies while you handle others.

The Physicist Rewards

Combat Ability: Spike or Astral Rebuke (your choice)
Artifact: Untapped Golden Earrings
Reset Item: x1
Source: 3,000

What to Do After Beating The Physicist

With The Physicist down, the Underpass breach is closed. The next big fight in the recommended boss order is The Co-Director. You can also go back and clean up any quests you missed in the Underpass.

Useful guides for nearby content:

Where to Play Control Resonant

Control Resonant is available on multiple platforms:

Frequently Asked Questions

How do I start The Physicist boss fight in Control Resonant?

Complete the main quest Recursions and Iterations, head to The Spire in the Underpass, and use Shift to climb the red blocks. Clear the top area, enter the Astral Plane, collect all three Astral Keys, and open the three locked doors to reach The Physicist.

Where are all three Astral Keys in the Underpass?

Each key is on a side path branching away from its corresponding locked door. The first is past a chest and wall-running route on the left. The second requires upside-down wall traversal to a bedroom area. The third is in an inverted corridor following a relocating chest.

How do I beat The Physicist in Control Resonant?

Run during the opening AoE chase, sprint in wide circles during debris volleys, and jump over ground sweeps to attack from the air. Kill all split forms and summoned minions immediately when they appear, then return to short attack windows followed by repositioning.

Should I choose Spike or Astral Rebuke after The Physicist?

Choose Astral Rebuke for melee and aerial combo builds. Choose Spike if you prefer autonomous summon pressure or already use a summon-heavy build. Both apply Astralized.

Can I leave and come back if The Physicist is too hard?

Yes. You can exit the Resonant route at any point. Spend Talent Points, upgrade your Aberrant, and return when you feel ready. The three-key section resets on re-entry.

What do you get for beating The Physicist?

You get a choice between Spike or Astral Rebuke, the Untapped Golden Earrings artifact, one Reset Item, and 3,000 Source.

Control Resonant: The Physicist Boss Guide – How to Beat The Underpass Resonant

Who Is The Physicist in Control Resonant?

When Can You Fight The Physicist?

Where to Find The Physicist – Location Guide