ARCUS, an abbreviation for All-Round Communication & Unison System, newly-made fifth-generation battle orbment developed by the Epstein Foundation in collaboration with the Reinford Group. Each unit has a built-in communications functionality. It's defining feature is the ability to link up with a partner to greatly enhance combat ability.
- Portable Communication: One of the primary functions to keep contact with fellow users anytime and anywhere.
- Orbal Arts: One of the primary functions for self-enhancement and combat magic by inserting quartzes into slots. For this new module, new types of quartzes are required to fit the slots in adjustment to the series' gaming balance.
- Master Quartz System: New Quartzes that are inserted into the central slot where it can level up and gain new abilities. In the new ARCUS II, the MQ slots were upgraded to insert up to two at once.
- Combat Link System: The module's unique distinction, allowing party members to 'resonate' with their partners during battle. Thereby, giving more coordinative tactics where one is assisted by their link partner to perform powerful follow-up attacks. The stronger the links become, the more abilities granted between different partners.
- Overdrive: A new function activated in Trails of Cold Steel II after Rean became an Awakener. Once activated, all party members are periodically given the advantages such as HP/EP/CP recovery, full status alleviation and all attacks/crafts perform 100% unbalance.
Trails of Cold Steel III introduces the successor to the ARCUS, the ARCUS II. Additionally of being able to perform all the functions of its predeccessor, it also allows usage of Brave Orders and setting of sub Master Quartz as well as taking photos, sending messages and installing apps such as Round of Seven and Pom! Pom! Party!.