The ring of charos (a)(i) is a ring of charos that has been activated during the Garden of Tranquility quest and has then been imbued in the Mobilising Armies minigame. The player must provide the ring of charos (a) to War-chief Reeves in the Officers' Tower. Garden of Tranquility must be completed in order to do so (if not, he will say you need to finish the quest before enchanting it.) The cost of doing so is 106,000 reward credits.
If lost, another can be received by pickpocketing Dr Fenkenstrain. However, it will lose its imbued status and will require a further 106,000 reward credits to be re-imbued.