CIO-class Mjolnir

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H4 MJOLNIR Counter Intelligence Operator.png
Production overview


Acheron Security

Testing site(s):

Gdynia, Acheron Fossae on Mars




Counter intelligence

Technical specifications
Designed for counter-intelligence operability in the Martian territory of Acheron Fossae.

The MJOLNIR Powered Assault Armor/CIO (Counter Intelligence Operator)[1] is a variant of the MJOLNIR Powered Assault Armor [GEN2].

Development history[edit]

The MJOLNIR/CIO variant was manufactured by Acheron Security and utilized by SPARTAN-IVs [2] and Counter-Intelligence Operators for Intel aquisition and strategic data conveyance deep within enemy territory. It was tested at Gdynia, Acheron Fossae on Mars.[1]

Several CIO-armored Spartans were deployed to Terceira, where they captured and transmitted information crucial to the recovery of the colony from Insurrectionist forces.[3]

In-game information[edit]

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Halo 4[edit]

Unlock: Spartan Slayer - Master commendation

  • Description: Designed for counter-intelligence operability in the Martian territory of Acheron Fossae

Available skins: WEB(Web), RUIN(Ruin) and RUSH(Rush)

Halo 5: Guardians[edit]

This armor set in Halo 5: Guardians permanently has the following

Unlock: Rare REQ card

  • Helmet Description: The neural interface bypasses in the CIO helmet allows the wearer to create custom synesthesis profiles to remap the the suit sensors with their own senses.
  • Body Description: CIO's niche is information denial missions: hunting down enemy scouts and preventing them from acquiring data of tactical or strategic importance.


List of appearances[edit]


  1. ^ a b Halo 4 Interactive Guide
  2. ^ Halo 4 pre-order
  3. ^ Halo 4: The Essential Visual Guide, page 148