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.
Character Specific Dialogue
When starting a Duel with Yami Yugi, Kaiba will say one of two announcements: "I will defeat you once and for all!" or "Every Duel I've fought has led up to THIS moment! The moment I finally take down Yugi Muto, and regain my top Dueling status! Let the epic battle begin!"
When he wins the Duel, he'll say "Now YOU will call ME the King of Games!
When starting a Duel with Joey Wheeler, Kaiba will say "I'll show this sniveling puppy that he's more bark than bite!"
When he wins, he'll say "Out-Dueling Joey Wheeler is no cause for celebration. I could've beaten him blind-folded."
When he loses, he'll say "So this is what it feels like being the worst Duelist in the world."
This is a reference to his loss to Pegasus in the anime in Duelist Kingdom.
When starting a Duel with Ishizu Ishtar, he'll announce "I don't believe in any of your destiny nonsense, is that clear?" followed by "The only thing I believe in is the power of my cards to take you down!"
When he wins, he'll say "You believed that destiny would leave you to victory." followed by "But I just proved that destiny is nothing but a joke!"
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!" If that player hasn't already Summoned "Blue-Eyes White Dragon" during that Duel, a cutscene of "Blue-Eyes White Dragon" being summoned will play afterwards.
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!" If that player hasn't already Summoned "Blue-Eyes Ultimate Dragon" during that Duel, a cutscene of "Blue-Eyes Ultimate Dragon" being summoned will play afterward.
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 "Kaibaman", he announces "It's like looking in the mirror! Here comes Kaibaman!"
Whenever Kaiba Summons "Vorse Raider", he announces "I Summon Vorse Raider!"
Whenever Kaiba Summons "XY-Dragon Cannon", he announces, "I Special Summon XY-Dragon Cannon!"
Whenever Kaiba Summons "XZ-Tank Cannon", he announces, "I Special Summon XZ-Tank Cannon!"
Whenever Kaiba Summons "YZ-Tank Dragon", he announces, "I Special Summon YZ-Tank Dragon!"
Whenever Kaiba Summons "XYZ-Dragon Cannon", a cut-in frame of Kaiba's face will briefly appear, and he'll announce "I special summon XYZ-Dragon Cannon!"
Whenever Kaiba activates the effect of "XYZ-Dragon Cannon", he announces "XYZ-Dragon Cannon's effect activates! Hyper Destruction!"
Most of the time when he declares an attack with that monster, he'll announce "XYZ-Dragon Cannon, attack! Unleash your firepower! Cannon Firestorm!"
Whenever Kaiba special summons "Vampire Lord", if that player hasn't already it during that Duel, a cutscene of "Vampire Lord" being summoned will play afterward.
Oddly, Kaiba doesn't make an announcement about the card before the animation plays, making "Vampire Lord" the first monster whose name isn't called before their animation, with the second being "Silent Magician LV8", when the latter is summoned by Yugi Muto.
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!"'
Whenever Kaiba activates "Soul Exchange", he announces "I activate the Spell Card, Soul Exchange!"