The second way to interpret the question is, Whats the optimal way to build my sideboard in a world where Dredge is popular
Child of Alara and Progenitus just do their own thing, and you build your deck behind them
Legendary Creature - Advisor Kor Ability Syn (CTRL to add secondary) cost reduction Agatha of the Vile Cauldron Activated abilities of creatures you control cost less to activate, where X is Agatha's power
The keyword abilities Descend Four, Descend Eight, and Fathomless Descent are similar to the Descend mechanic in that they care about permanents in your graveyard
Law, Luffy, Kaido, and Crocodile also marked the first dual-color Leaders
For more details on importing Japanese cards, see our guide to buying One Piece cards from Japan