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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 2026-07-26)

What players say

Steam review score and the most-helpful voices, which may include critical ones. Data as of 2026-05-20.

79.0%positive3,032 reviews
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 count fetched 2026-07-11 13:09 UTC · history via SteamCharts.

65playing at last check
7524-hour peak
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 2026-07-25.

5achievements
36.5%median completion
18.9%rarest: Build the Artillery Unit
79.8% of players 64.7% of players 36.5% of players 25.0% of players 18.9% of players 79.8% 0% most earned rarest
Almost everyone has
79.8%Into the Deep End — It Begins.... Your first steps on Treasure Island
64.7%And so it begins.... — Survive your first day on the island
36.5%Didn’t go as planned… — Hidden achievement
Rarest badges of honor
18.9%Build the Artillery Unit — Hidden achievement
25.0%Avid Listener — Listen to a custom music track
36.5%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 2026-07-26 08:39 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 Australia US EU UK≈$24

Cheapest → most expensive, converted to USD at ECB reference rates (2026-07-24). Relative comparison only.

$0 $25 $50 07-11 07-13 07-16 07-19 07-22 07-26

Latest official news

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

Jul 24, 2026
World Reveal of CERC Ops This Saturday!

A New Way to Monitor the Battlefield This Saturday, during the 100th episode of CERC HQ , we will hold the world reveal of CERC Ops , a new tactical companion built specifically for Cepheus Protocol.

Jul 20, 2026
Massive Performance Gains and Smarter Fog of War Are Coming

These transmissions come directly from the front. The battle for the Bay Area has begun. Core Improvements and Community Audit As outlined during CERC HQ on Saturday, we are continuing to refine the c

Jul 12, 2026
2026.7.11 AI, Performance & Helicopter Systems Update on Experimental

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

Jun 20, 2026
2026.6.19.5 Discord Integration Fixes + Launcher

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

Jun 19, 2026
2026.6.18.2 Weather System, Discord, Vehicles, and Pandemic Fixes

The virus is loose across the Bay Area. Flashpoints are erupting across the peninsula 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 2026-05-20.

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
Estimated owners200,000 – 500,000 (SteamSpy)
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