- "jOkEr★Is nOt A ghOst! JoKeR iS a★CaRdIaN!"
While fighting for truth, justice, and the onion way, the vigilant members of the Star Onion Brigade find themselves at odds with Nanaa Mihgo, a professional criminal. After spotting her snooping around Karaha-Baruha's abandoned manor, they ambush her with stink bombs and cause her to drop a Mana Orb, a device used to power Cardians. Emboldened by this victory, they plan to catch Mihgo inside the house itself.
Their triumph sours, however, when Nanaa turns the tables by locking the Star Onions in Karaha-Baruha's manor. Fearful of ghosts in the dusty mansion, they fumble about in the dark. In the process they stumble across the dormant body of Joker, who absorbs the Mana Orb they carry and rises to meet them. With Joker's assistance the Onions are able to go outside. They ask Joker if the manor was his home and in the irregular cadence of a Cardian he replies that it is not. His memory is not functioning well so the Onions invite him to come with them.
The wealthy Tarutaru trader from whom Nanaa Mihgo had stolen the Mana Orb soon learns of the Brigade's involvement and demands that the Star Onions return his property. When they point out that the Mana Orb has been absorbed by Joker the merchant calls for the Cardian to be dismantled. Joker wanders off before his orb can be taken and the Onions send a helpful adventurer to look for him.
Joker faces the Onions' assistant outside Karaha-Baruha's manor. He begins to speak without artificial tones and asserts that although Cardians must be willing to die for their masters he cannot allow himself to be disassembled. He implores the adventurer to help him search Toraimarai Canal for the reason he is compelled to survive.
They subsequently discover an inactive Cardian control card labeled as Joker's. Seeing this, Joker loses all traces of his mechanical personality and remembers his true identity and purpose. He had been created by Karaha-Baruha during the Crystal War using a portion of the mage's own spirit. The magics animating a Cardian unravel when its creator dies, but Karaha-Baruha knew that forcibly reactivating a dead automaton could also draw its maker back from death. Anticipating that he would be lost in the Battle of Windurst, the summoner had prepared Joker to give himself a second chance to set things right.
With the remnants of Karaha-Baruha awakened inside him, Joker bids farewell to the Star Onion Brigade and assumes leadership of the rogue Cardians in the Horutoto Ruins. From there he manipulates the course of events in Windurst, indirectly helping Ajido-Marujido escape from prison and detaining the Star Sibyl at the Full Moon Fountain. With this valuable hostage, he is able to convince the Federation's brightest minds to assist him in the completion of Karaha-Baruha's work.
Joker relies on Ajido-Marujido to lure to the Fountain a creature called the bearer of darkness, which contains the rest of Karaha-Baruha's spirit as well as the lost energies of Fenrir. When the shadowy entity arrives Joker sacrifices himself and all his Cardian followers to combine with the bearer into a single source of light. The Star Sibyl then uses this energy to revitalize the Full Moon Fountain and restore Fenrir to its place as Windurst's guardian. Karaha-Baruha's grand design to defend his nation is thereby completed.
Afterward Joker's powerless Mana Orb is brought to the Star Onion Brigade, who mourn the Cardian's loss. He had promised to return to them and they cannot accept that he is truly gone. His spirit appears before them, however, and resolves to watch over them and the city. The Star Onions, in turn, restate their own commitment to vigilance.
Joker appears in Trading Card Game as part of the "Earth" set.