High School DxD EX

High School DxD EX (ハイスクールD×D EX Haisukūru D×D EX) is a six part special novel released with the Blu-Ray volumes of the third anime series, High School DxD BorN.

Chapters

 * 1 Crimson-haired Sekiryuutei
 * 2 Invaders from Another World
 * 3 A New Church Trio
 * 4 Crimson Will
 * 5 The Forbidden United Front
 * 6 And so, to Tomorrow...

Summary
The Occult Research Club faces off against invaders known as Underworld Lifeforms led by Loki that has travel from the future, however also from the future comes a surprise visit by Issei's children.

Antagonist

 * Loki (ロキ): The Evil God of Norse who returns to the past after cursing Asia. He teams up with the beings from the other world UL to change the past.
 * Ruma Ydura: A being of the Other world Mythology and one of the Four Generals 'Invade Fanatics'.
 * UL: Mechanical beings from the other world. They invaded the world the Three Factions resides in the near future before travelling into the past with Loki.

List of Equipment

 * Boosted Gear Diabolus: Also known as the Gauntlet of the Red Dragon Emperor Crown Prince is an artificial Longinus created by Kurenai based on the the Boosted Gear.
 * Durandal IV
 * Galatine III: An alchemy-metalurgical crafted version of Galatine, it is used in tandem with Ex's Power of Destruction.
 * Gigantis Maiden Robe: An Artificial Longinus with Fafnir as its power source.
 * Kashuu Kiyomitsu and Yamatonokami Yasusada: Two Holy Swords wielded by Shin. Its name is taken from the actual swords used by the historical Okita Souji.

Trivia

 * The Nekomata sisters, are technically sibling-cousins, being Half-sisters and cousins at the same time. Despite being born on the same day, they are not considered twins.
 * It's revealed that Ex is just as perverted as his father but is very secretive about his desires unlike his father who is very open about them.