What to know
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Protoset is an Operator promotion material used for higher-tier promotions (E3/E4) and raising level caps.
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The most reliable repeatable source is Protocol Space: Promotions at Threat Level 3 and 4, which costs Sanity to run.
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You can also get Protoset from exploration chests and some mission rewards, but these are less predictable.
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Rare gather nodes matter long-term because many key upgrade materials are time-gated with long respawns (around 3 real-life days).
A lot of your progression pressure in Arknights: Endfield shows up when you start pushing Promotions III and IV, because that’s where Protoset becomes a core requirement. The good news is that the game gives you a repeatable farming lane (Protocol Space) and a “while-you-play” lane (exploration and missions), so you can combine both for steady stockpiles.
| Topic | Quick details |
|---|---|
| Primary farm | Protocol Space: Promotions at Threat Levels 3 and 4 (Sanity required). |
| Secondary sources | Story/side missions can reward Protoset; exploration chests can contain it. |
| What it’s for | Promoting Operators to higher tiers and increasing their level cap. |
| Why it feels “slow” | Some upgrade materials are tied to limited map nodes with long respawn timers (around 3 real-life days). |
Where Protoset fits in Operator promotions
Promotion costs ramp up fast once you reach the tiers that start consuming Protoset. For reference, Promotions III and IV explicitly require Protoset in sizable amounts, along with other materials and T-Creds.
| Promotion tier | Level cap | Protoset needed | Other listed costs |
|---|---|---|---|
| Promotion III | Lv.80 cap | 24 | 5 Ruby Bolete, 18k T-Creds. |
| Promotion IV | Lv.90 cap | 36 | 20 Metadiastima Photoemission Tubes, 8 Bloodcap, 100k T-Creds. |
How to get Protoset from Protocol Space: Promotions
Step 1
Go to Protocol Space and select the Promotions activity, since Protoset is awarded there at higher difficulty.
Step 2
Set the activity to Threat Level 3 or Threat Level 4, because these are the Threat Levels that list Protoset as a reward. At the same time, choose Options from the Reward Preview.
And make sure the Protoset reward is selected.
Step 3
Spend the required Sanity to enter and complete the run.
Then make sure you claim rewards at the end (the reward is tied to completing and claiming).
Step 4
Repeat as Sanity allows, and treat it like a routine farm whenever you’re preparing multiple Operators for Promotions III/IV.
How to supplement Protoset through exploration and missions
Step 1
While exploring Talos-II, open any chests you come across, since Protoset can appear in chest loot.
Step 2
Clear story missions and side quests as you progress, because some missions can reward Protoset upon completion.
Step 3
Build a habit of checking rare-node icons on the map when you unlock a new area, since time-gated materials can bottleneck promotions if you ignore them early.
Protoset farming habits that prevent bottlenecks
Rare growths/ores appear in limited spots, have distinct map icons, and can be tracked directly on the map, so you can keep tabs on what’s available. Because the full refill cycle can take around 3 real-life days, missing cycles can quietly slow down your Operator progression later.
If you want Protoset on demand, run Protocol Space: Promotions at Threat Level 3/4 whenever your Sanity budget allows, then top it up through normal exploration and mission completion. Keeping an eye on time-gated resource nodes helps you avoid the moment where promotions outpace your material income.
