[quote=@Kaggs]
imo having this kind of easter egg hunt for strong cards might force a lot of us to write similar characters, like "whats to be the king of kings". It's not like there's a lot of unique reasons a person might want to collect these kind of cards.
[/quote]

Keep in mind the Ante rule is a sideshow at best; My main suggestion was gathering everyone in the same city, presumably a hub for duelists. The reason you have to come to the city is up to your character.

Battle city's come up a lot, but I'll draw from it again for another example. A lot of characters had different motivations in it:

-Atem was looking for his memories
-Jounouchi wanted to prove he was worthy of holding Red-Eyes by becoming a true duelist
-Mai was fighting to prove she was an independently strong duelist and didn't need to rely on Yugi's support network
-Bakura wants to obtain the Millenium items
-Marik wants to kill Atem
-Rishid follows Marik
-Ishizu wants Marik to not kill Atem
-Kaiba just wants to flex on Atem

And this is just the quarter-finalists. Most other competitors came to the tournament just to win the gods and rare cards, yes, but none of those made it into the finals because they're not interesting motives. That's what I'd be looking to emulate; Have players come up with their own side-stories to get them into the city and into the story.