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Cepheus Protocol

Cepheus Protocol

Cepheus Protocol is an Open World RTS Military Survival Game. Play as the CERC hunting Patient 0, maintain Quarantine camps, fight dangerous mutations & Rogue Civilian Combatants . There’s nobody else coming, it’s up to you now.

Released May 15, 2020 Developer Halcyon Winds Platforms Windows SandboxZombiesRTSSurvivalPost-apocalyptic
View on Steam ↗ $19.99 (US · as of 2026-09-05)

What players say

Steam review score and the most-helpful voices, which may include critical ones. Score via Steam as of 2026-09-02 · quoted reviews as of 2026-05-12.

75.4%positive3,757 reviews

What reviewers agree on

Praised
Criticised
Bar length = how many of the 104 reviews raise the point On criticised points, the pale part = reviewers who still recommend the game Select a point to see the exact counts and what reviewers wrote.

Counted across 104 English reviews, sampled to match this game's 75.4% positive rating · as of 2026-05-12

Recommended · 32 found this helpful

“TLDR: Buy now? No Buy in the next six months: Maybe Buy in a year: Yes It's an early access game it's had a rough development cycle and only really in the last 1.5 years and have the devs actually started refining the game. choosing to rebuild the game from the ground up, moving…”

— a player, Steam review · 45 hrs played
Recommended · 12 found this helpful

“For all the negative votes, you didn't read the important pop up note on the right side of the main menu stating to play the 'Legacy Version' if you want to "grasp the direction the game is heading". The version that is uploaded right of the bat is the new game being built from…”

— a player, Steam review · 85 hrs played
Not recommended · 35 found this helpful

“[code]This game would be a dream come true for me, but sometimes you have to face the facts: it's a 6 year old game with bugs, glitches, unfinished maps, unfinished builds, buttons on the UI that dont function, awful sound design and an achievement you cant get because there's…”

— a player, Steam review · 12 hrs played
Read more reviews ↗

Player activity

Monthly average concurrent players. Live data self-collected from the Steam API · history through 2026-06 via SteamCharts.

378all-time peak
0 100 200 2021 2022 2023 2024 2025 2026 121 avg · Oct 2021

Achievement stats

Global completion rates across all Steam players — a data view of how far people actually get. Source: Steam official stats · as of 2026-09-05.

5achievements
35.2%median completion
19.2%rarest: Build the Artillery Unit
80.3% of players 65.0% of players 35.2% of players 26.7% of players 19.2% of players 80.3% 0% most earned rarest
Almost everyone has
80.3%Into the Deep End — It Begins.... Your first steps on Treasure Island
65.0%And so it begins.... — Survive your first day on the island
35.2%Didn’t go as planned… — Hidden achievement
Rarest badges of honor
19.2%Build the Artillery Unit — Hidden achievement
26.7%Avid Listener — Listen to a custom music track
35.2%Didn’t go as planned… — Hidden achievement

Price tracking

US-region pricing (USD), sampled twice daily by our own tracker since 2026-07-11. Steam prices vary by region — always confirm your local price on Steam.

$19.99current · sampled 2026-09-05 20:23 UTC
$15.99lowest since tracking began2026-07-13
US19.99 USD
EU20.49 EUR
UK17.75 GBP
Australia28.50 AUD
Canada23.99 CAD
Japan2,600 JPY
Brazil67.99 BRL
China77.00 CNY

Regional prices at last sample, in local currency — Steam sets each region's price independently.

China≈$11 Brazil Japan Canada US Australia EU UK≈$24

Cheapest → most expensive, converted to USD at ECB reference rates (2026-09-04). Relative comparison only.

$0 $25 $50 07-11 07-21 08-01 08-13 08-24 09-05

Latest official news

Developer announcements via the Steam news API — links go to the original posts. More across all games on the news hub.

Sep 04, 2026
2026.9.4 Experimental Patch Notes & September Development Update

The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in

Aug 21, 2026
2026.8.21.1 Experimental Patch Notes & August Development Update

The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in

Aug 13, 2026
2026.8.13.1 All Branches

The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in

Aug 05, 2026
2026.8.4.1 + 4.2 Experimental and Normal Patch Notes

The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in

Aug 01, 2026
2026.7.31.3 Quality of Life Update Live + GPU Fog of War Tonight on Experimental

The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in

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Screenshots

Official Steam store screenshots — click any shot to enlarge.

Facts & details

From the Steam store record, snapshot 2026-05-12.

GenresAction, Adventure, Indie, Massively Multiplayer, RPG, Simulation, Strategy, Early Access
Player tagsSandbox · Zombies · RTS · Survival · Post-apocalyptic · Building · Strategy · Gore · Open World · Singleplayer · Diplomacy · Indie (SteamSpy community voting)
FeaturesSingle-player · Multi-player · Co-op · Online Co-op · Steam Achievements · Steam Trading Cards · Steam Workshop · Adjustable Text Size
LanguagesEnglish * , Simplified Chinese, Korean, German, Japanese, Russian, Spanish - Spain, Portuguese - Portugal, French *
Achievements5
Official sitehttps://cepheusprotocol.com/
Minimum system requirements (PC)

Minimum: Requires a 64-bit processor and operating system OS: Windows 10/11 (64-bit) Processor: Intel® Core™ i5-4500K Memory: 8 GB RAM Graphics: NVIDIA GeForce 1060 GTX or AMD Radeon Equivalent 4 GB DirectX: Version 12 Storage: 8 GB available space Sound Card: Direct X Compatible Additional Notes: **recommended SSD install for optimal performance