The second of the Four Horsemen of the Apocalypse, named War. He represents war, and his horse is colored "fiery" red. He holds a great sword upwards as though ready to battle or mass slaughter. The sword is meant to suggest that blood will be spilled. The great sword being held upwards can also be viewed as a declaration of war, as typically, crossed swords held upward in herarldry signify entering in battle. He takes peace from the Earth and allows men to kill one another.
"When He broke the second seal, I heard the second living creature saying, “Come.” And another, a red horse, went out; and to him who sat on it, it was granted to take peace from the earth, and that men would slay one another; and a great sword was given to him."
"One of the four horsemen of the apocalypse. He rides on a red horse and holds a great sword. He has the power to take peace from the earth and make men to kill each other."
—Shin Megami Tensei III: Nocturne Compendium
Red Rider appears as one of the Candelabrum holders sent by Lucifer to test the Demi-fiend, possessing the Candelabrum of Insight. He first appears with the other Horsemen of the Apocalypse when the Demi-fiend first ventures into the Third Calpa. After defeating White Rider, Red Rider will appear outside the Terminal in the Great Underpass of Ginza. As with the battle with White Rider, a Dis with the Stone Gaze skill can inflict the Stone status on the Powers summoned by the Red Rider for support. They will waste press turns for as long as they remain on the field. Unlike the White Rider, the Red Rider cannot use the Dekaja skill, allowing the party to buff as necessary. Defeating the Red Rider in battle will get the player the Candelabrum of Insight.
After being defeated and once the player reaches level 55, Red Rider can be fused in the Cathedral of Shadows on the New Kagutsuchi phase if the player possesses a Deathstone, a special item found only in the Labyrinth of Amala. Red Rider can be fused by any combination of demons resulting in a Fairy.
Red Rider appears as the summon orb boss of the Suginami Tunnels silver-level instance. He also appears as a boss within the Chain of Curse Deep Docks instance and a boss of the TR-Route of Denshi Kairo, through which the ability to fuse him can be obtained. He is a special triple fusion of White Rider, Power, and Koumokuten.
Red Rider is one of seven fiends available to fight as an optional battle. He is found in Kasumigaseki, in the underground area that requires ID Card Lv3 to access; for this reason, he can only be fought on the Neutral route. He has a 1/256 chance of spawning behind the door that requires 100 Luck to open; if he doesn't show up, a message displays pops up saying that nobody is present. His Almighty-spam mode is set by Fire resistance. However, unlike other Fiends, he will use his Almighty attack (Antichthon) frequently even if the party does not resist Fire or Physical. Defeating him awards you with a Soma, 10 of each incense, and the ability to obtain him through Special fusion.
Red Rider is fought alongside the other three in the Challenge Quest, Errand for the Apocalypse. Belial has sealed the four in a Domain found in Infernal Tokyo's Ikebukuro. They are far weaker than they are when encountered normally, that does not make them any less threatening. If Flynn makes any attempt to challenge them before accepting the quest, the Fiends will eject him from the domain. Completing the quest grants Flynn the Peacemaker, which is only surpassed by the plasma gun in terms of raw power.
Red Rider, along with all the other Fiends, is encountered in Twisted Tokyo. Unlike previous games, they are not secret bosses and do not require tediously searching and resetting to encounter. Each Fiend starts with 3 Press Turns and gains one additional turn for every 2 Twisted Tokyo cycles, eg 4 turns on TT3, 5 turns on TT5, etc, in addition to increasing in level by ~75 levels each cycle; completing the first run and reaching higher cycles of Twisted Tokyo requires the "Eternal Torus" item from the "Depths of Twisted Tokyo" DLC ($1.49), and while not technically required the "Level Cap Unlock" DLC (free) is also needed due to the high enemy levels. Fiends must be defeated within 10 turns or Nanashi gets evicted to the dungeon's entrance, however the Fiend's HP does not recover when this happens. The Fiends drop a number of items equal to the current Twisted Tokyo cycle, up to 6 items at Twisted Tokyo 6; each has the possibility of dropping Incense, Armor Boost Kits, Strategems, Compendium Tickets, and a piece of unique equipment. Red Rider is encountered on B9F and drops the Chaos Sword, and is fought at level 946 on cycle 9.