Yugi's eternal rival and president of KaibaCorp - the world's leading gaming conglomerate. Extremely proud and confident, Kaiba will stop at nothing to become the greatest Duelist in history. Kaiba's signature monster is the legendary "Blue-Eyes White Dragon".
When Yu-Gi-Oh! Duel Links is started after it is successfully downloaded in its entirety, Kaiba will appear confronting Yami Yugi, declaring that when he (Kaiba) defeats him, Yugi will have to call him the King of Games. He then wonders aloud if Yugi even has the cards to confront him. Depending on the player's choice, either he or Yami Yugi can then be utilized in the subsequent tutorial Duel.
After the player concludes their initial in-game tutorial, Kaiba makes an appearance, broadcasting a global announcement across the world of Duel Links. He declares that the Duelists must have realized where they've arrived by now, before revealing that the Duelists present are all here in order to test their skills in the next evolution of Dueling. He proudly states that this world is the perfect place to determine who the real champion is, before rhetorically asking who will wear the crown as Duel World King. Kaiba then reveals that Duel World is divided into different Stages, and he prompts Duelists to reach the final stage to "claim the throne," defeating all who stand in the way of their dreams. Concluding his announcement, he invites Duelists to come to Duel World for their greatest challenge, to test themselves to their breaking points, and dares them individually to become the Duel World King. He then disappears in laughter.
At this point, if the player had chosen Kaiba for their tutorial Duel, he will immediately reappear in Duel World; otherwise, he will only make his next appearance after the player reaches Stage 15. In either case after his appearance, he will declare that everything is proceeding as planned, since the Duelists he invited will help complete Duel World with every Duel they engage in. He then reminisces of Yugi, declaring that both he and Yugi will have their final Duel in this world. (Kaiba's dialogue ends at this point, unless the player had chosen Kaiba as their initial character, in which case Kaiba additionally declares that Yugi will fall against his trusted ally: "Blue-Eyes White Dragon".)
Yami Yugi route
If the player chooses Yami Yugi as their initial character in Yu-Gi-Oh! Duel Links, they will also encounter the following instances of unique dialogue, as they attempt to unlock Seto Kaiba as a playable character.
Until the player has already defeated Kaiba at least once in a non-tutorial Duel, whenever they challenge Kaiba to a Duel, Kaiba declares that only the one Duelist who crushes all foes and snatches victory will earn the title of Duel World King. He then states that the player will unfortunately not be that Duelist, since there can only be one winner: himself. He concludes his dialogue by prompting the player to Duel him.
When Kaiba loses to the player for the first time (in a non-tutorial Duel), he growls before admitting that since only the victor has the right to speak, he'll remain quiet in the meantime. He then reminds the player that this is only the start of their journey to become the Duel World King, before bursting into arrogant laughter.
After the player redeems their final unclaimed reward for Seto Kaiba's Character Unlock Missions, they will encounter Kaiba again, who explains that since his path to the future was clouded and unclear, he created the world of Duel Links as an arena for all Duelists in order to illuminate that path. He goes on to declare that he will rule this world as the King of Games when he defeats Yugi, and that "Blue-Eyes White Dragon" will guarantee his victory, before bursting into prideful laughter.
Begins Duel with the Field Spell Mountain activated.
This turn, the ATK of all face-up monsters on your field increases by the number of monsters of Level 5 or higher on your field times 300. This skill can only be used once per turn.
Draw Sense: High Level
Can be used each time your Life Points decrease by 1800. In the Draw Phase, instead of doing a normal draw, draw a random level 7 or more monster.
If your Deck has 3 or more Level 5 or higher monsters with different names, you will have improved chance of having a Level 5 or higher monster in your starting hand.
Card Specific Dialogue
Whenever Seto Kaiba Summons "Blue-Eyes White Dragon", a cut-in frame of Seto Kaiba will appear, where he'll announce "Not a single card can stand up to this!" followed by "I call on Blue-Eyes White Dragon!"
Most of the time when he declares an attack with that monster, he'll announce "Blue-Eyes! Lay waste to your enemy!" followed by "White Lightning!"
Whenever Kaiba Summons "Blue-Eyes Ultimate Dragon", a cut-in frame of him will appear, where he'll announce "Witness the incredible creature of unsurpassed power!" followed by "Blue-Eyes Ultimate Dragon!"
Most of the time when he declares an attack with that monster, he'll announce "Prepare for annihilation! Blue-Eyes Ultimate Dragon, attack!" followed by "Neutron Blast Attack!"
Whenever Kaiba Summons "Vorse Raider", he announces "I Summon Vorse Raider!"
Whenever Kaiba activates "Enemy Controller", he announces "I activate Enemy Controller" followed by "Enter the code! ←→AB!"
Whenever Kaiba activates "Polymerization", he announces "If you didn't already realize how much better I am than you, you'll find out now! I activate Polymerization!"