Onmoraki
Onomatokage
Onomatopaira
Onomatopia
Onomatopickup
Onslaught of the Fire Kings
Ooguchi
Ookazi
Oops!
Opening of the Spirit Gates
Opera the Melodious Diva
Oppressed People
Opti-Camouflage Armor
Opticlops
Option Hunter
Option Token
Oracle of the Herald
Oracle of the Sun
Oracle of Zefra
Orb of Yasaka
Orbital 7
Orbital Bombardment
Orbital Hydralander
Orca Mega-Fortress of Darkness
Orcust Brass Bombard
Orcust Crescendo
Orcust Cymbal Skeleton
Orcust Harp Horror
Orcust Knightmare
Orcustrated Attack
Orcustrated Babel
Orcustrated Core
Orcustrated Einsatz
Orcustrated Release
Orcustrated Return
Orcustrion
Ordeal of a Traveler
Order of the Queen
Order to Charge
Order to Smash
Orea, the Sylvan High Arbiter
Orgoth the Relentless
Orichalcos Shunoros
Orichalcos Sword of Sealing
Orient Dragon
Origami Goddess
Original Bamboo Sword
Original Sinful Spoils - Snake-Eye
Orion the Battle King
Orphebull the Harmonious Bullfighter Bard
Oscillo Hero
Oshaleon
Ostinato
Otherworld - The "A" Zone
Otohime
Otonari Thunder
Otoshidamashi
Out of the Blue
Outburst Dragon
Outer Entity Azathot