Bishamon Sword (毘沙門剣, bishamonken) is the ultimate sword bearing the name of the God of War. It has extraordinarily high damage that can kill nearly any Genma in one strike. It lacks magic attacks; Instead, it has a special 360 degrees slash which is far more powerful than the normal strike and eliminates most enemies in one hit, even from full health.
- Bishamon Sword is hinted to be the first of the most powerful Oni sword/weapon in existence yet there are several weapons who rival its might. One can assume the Oni crafted several of these ultimate weapons with the intentions of them being wielded by each individual Oni warrior.
- Bishamon Sword has three orbs of element in it. The blue orb for Raizan, green orb for Shippuu and red orb for Enryuu. The meaning or purpose behind these orbs is never explained; one can guess they are the elemental blend of each weapons orbs which gives the sword its infinite power.
- The Bishamon Sword can unlock (1-3 orbs) the blue orbs, red orbs and green orbs in Onimusha: Warlords. While in Onimusha 3: Demon Siege, you can't unlock the light orbs, cyan orbs and light-red orbs because the sword is differrent.
- The sword is called the 'Fallen Angel' in Onimusha: Dawn of Dreams. Can only be equiped by Hideyasu Yūki.
- This sword along with the holy Excalibur make up the dual-sword combination Basara use by Musashi Miyamoto during his brief appearance in Onimusha Blade Warriors.
- In Onimusha Warlords for PS2 and The Remaster there are differences between the two texts when talking to the statute holding the Bishamon sword. However they both refer that the sword is powerful to kill Oni Warriors and Genma alike, this might explain why the Sword is sealed away within the demon world. With the only way to obtain it is from going deep within the Dark Realm and obtain the Bishamon Ocarina to unseal it once again.