- "The weak can't be trusted."
- — Jack-O
During Armored Core: Nexus, Jack-O was known for being a top Raven (#5) as well as a radical who believed in the neutrality of the Ravens' Ark in the corporate affairs. After discovering illegal activities between the Ark's administrators and Mirage, Jack forcefully took control of the Ark, expelled all administrators (Operators included), radically restructured the organization, and kicked Evangel out of the organization for taking direct contracts.
He disappeared after the attack of the unmanned suicide weapons, but in response to the formation of Alliance, Jack-O created Vertex to oppose them, all the while searching for a Raven who could stop the Pulverizers. Unlike the Alliance who tries their best to keep their Ravens alive in the conflict with betrayal being the only thing that is punishable, Jack-O (and Vertex by proxy) shows no mercy to fellow Ravens who fails to live up to his expectations mainly due to the Pulverizer's adaptive data: a dead Raven at the hands of a Pulverizer will mean future Pulverizers are even more lethal. He either dies or goes missing in the various endings.
In Last Raven, he is fought in "Attack Invading Force" and "Defeat Jack-O". He appears in the cut scenes of "Distribution Center Recon," "Pursue Withdrawing MT," "Underground Investigation," and "Shutdown Internecine".
Jack-O pilots a heavyweight AC called Foxeye, which has amazing firepower coupled with great mobility at the cost of defense. Foxeye is equipped for middle to long range combat.
It's best to use heavy weaponry on him. However, you must be wary that you don't get caught in his chain of attacks. Despite impressive mobility for its class, the Foxeye has relatively low defense in comparison with other heavy AC's. Jack-O's AC is especially susceptible to laser weapons, especially high lasers. The fastest and simplest way to defeat him is to use a lightweight AC with MS response capability, low energy drain and a high laser weapon, preferably the Karasawa high energy rifle. With ample dodging it should be an easy win.
Another strategy is to use heavy AC with large aperture laser cannon or an large GERYON/KRSW combos as an ambush for beginners.
- Head: H07-CRICKET
- Core: C04-ATLAS
- Arms: CR-A72F
- Legs: LH13-JACKAL2
- Booster: B02-VULTURE
- FCS: MONJU
- Generator: KUJAKU
- Radiator: FURUNA
- Inside: I07D-MEDUSA2
- Extension: NONE (ANOKU in Nexus) (CR-E92RM3 in "Shutdown Internecine" & "Defeat Jack-O")
- Back Unit R: CR-WBW94M2 (CR-WB85MPX in Nexus)
- Back Unit L: CR-WBW94M2 (WB18M-CENTAUR in "Defeat Jack-O")
- Arm Unit R: WH04HL-KRSW
- Arm Unit L: CR-WL95G
- Jack-O's name possibly comes from Jack-O-Lantern, a reference to the head piece he uses which bears a striking resemblance.
- Jack's voice actor in Nexus is different from that of his Last Raven one.
- In Armored Core: Nexus, if the player fails the first mission, "Attack Mirage Search Team" and then play it again and also fail to destroy the enemy, Jack-O will appear and finish the mission for you.
- Foxeye is one of the ACs made into a Model Kit.