Self-mill and dredge decks usually mill a good part of their library and win with cards like Vengevine, Bloodghast, and Prized Amalgam
Ironic Echo: In season one, Kaiba threatens that he'll fall from the castle's battlement if Yugi wins the duel, so Yugi forfeits in fear that Yami Yugi would finish Kaiba off
Maybe try forcing it with 'This Town Is Too Small' to ramp
Thematic Deck-Building One of the joys of Commander is the freedom to create decks that reflect your favorite themes and stories
instead, they take a page from the anime-exclusive Dark Synchro monsters with their Extra Deck members being summoned by using the level difference of two monsters on the field
In your hand, library, or graveyard they have the casting cost of both sides, but on the field they have the mana value of their unlocked doors