Barret Wallace #8 (Magic Final Fantasy Art Series | Magic Cards) prices are based on the historic sales
Cards like Omastar, Poliwrath, and Kingler may not have the highest raw damage, but their abilities make them effective in a well-rounded strategy
Events may offer bonus Wonder Picks that have special cards, or they may add new solo battle challenges that unlock promo packs when you complete them
Etherium-Horn Sorcerer can do all of this in one card
He also supplements his Deck with "Rank-Up-Magic" cards such as "Rank-Up-Magic - The Seventh One", which lets him Rank-Up his "Over-Hundred Number" from the Graveyard, field or Extra Deck and "Rank-Up-Magic Quick Chaos", a Quick-Play Spell Card which allowed him to instantly Rank-Up his "Number 73: Abyss Splash" into "Number C73: Abyss Supra Splash"
As for the theme, its difficult to call