The Radiation Host is the fifth story boss, in the lower Containment Sector. It is covered in Glowticks that heal it, so shooting it first is wasted ammo. Pull each Glowtick off with the Grappling Hook and kill it with the Knife until none are left, then keep your distance and shoot; grenades are ideal because it is slow. Avoid the radiation zone its charge leaves behind. You need the Radiation Protection Mod to get there, and update 1.014 fixed leftover bugs hurting you after the fight.
Where to find the Radiation Host
The fight ends Part 5 of the walkthrough. After the room with the containment tank, where Glowticks drop through the roof, take the elevator shortcut to the second Safe Room, restock, then go down the stairs and through the broken wall.
| Details | |
|---|---|
| Boss order | 5th of 7 story bosses |
| Location | Lower Containment Sector |
| Required | Radiation Protection Mod (to reach it), Grappling Hook (to fight it well) |
| Reward | Vault Key; the third SCU is just past the arena |
| Achievement | Radiation Contained |
Get the Radiation Protection Mod first
The mod is the only mandatory Suit Mod in the game, and it is not in the Containment Sector. It is in Factory East, behind the Basement Keycard you pick up at the Containment Sector's exit to Factory East.
- Take the Basement Keycard from the body near the exit and extend the bridge shortcut with the panel.
- In Factory East, clear the Security Turret encounter and keep heading left and down to where you entered Waterworks with the Supervisor Key.
- Open the Basement Keycard door and survive a Husk Brute plus four Infected Reactor Workers.
- Buy the mod through the left door for 4 Energy Cells and equip it at any Restoration Pod.
Its attacks
| Attack | What it does | How to answer |
|---|---|---|
| Glowtick armour | Glowticks on its body heal every hit you land | Hook them off and kill them before you deal damage |
| Glowtick summon | Sends out more Glowticks | One Knife hit kills each one |
| Charge | Rushes you and leaves a radiation zone | Roll sideways; stay out of the zone afterwards |
| Melee | Slow close-range swing | Rarely a threat if you keep your distance |
Step-by-step strategy
- Rest and restock at the second Safe Room shortcut. Bring grenades.
- Do not shoot the boss yet. Target a Glowtick on its body with the Grappling Hook to pull it off.
- Kill the Glowtick with the Knife. Repeat until its body is clear. This is the step that makes the fight winnable.
- Back off and shoot. Throw grenades freely: it moves slowly, so they almost always land.
- When new Glowticks appear, knife them before they reach the boss.
- Roll away from every charge and do not stand in the radiation it leaves.
After the kill, take the Vault Key, go through the door on the right and down the ladder to the SCU. Activating it gets the Central Elevator running.
What update 1.014 fixed in this fight
- Bugs that fall off the boss now die properly and no longer damage you after the boss is defeated.
- The boss is easier to scan while covered in bugs, so you can add it to the Logbook.
- Focused Grapple targets are easier to see, which makes pulling Glowticks off far more reliable.
If the fight felt broken before October 7, update and try again. Full details are in the patch notes.
Frequently asked questions
Why does the Radiation Host keep healing?
The Glowticks on its body heal it whenever you deal damage. Remove them with the Grappling Hook first.
Can I beat it without the Radiation Protection Mod?
You would take radiation damage the whole way in. The mod is required in practice and is the only mandatory Suit Mod.
What comes after the Radiation Host?
The third SCU and the Central Elevator to the Lower Levels, home to the last two bosses. See the boss guide.
This page only uses details from official store pages, developer statements and hands-on press previews. Anything unconfirmed before the October 1, 2026 launch is left out and will be added once verified. Last research pass: October 9, 2026.
Sources
References and further reading for this article.
