Several Pokmon cards found in the upcoming expansion - not just the ex kind - enable players to obtain, move and expel energy cards to gain an advantage
When you are reliably finding one and winning with it when you just have three then you don't overly need a 4th
Aragorn, Hornburg Hero Aragorn, Hornburg Hero lets you crash in with creatures much more safely thanks to first strike, and gets ridiculous with double strike
FBB Plateau (German) 199,99 Plateau FBB from Magic: The Gathering
The buyer still has to provide a card of the same rarity they either dont want or need, while the seller receives a card they can resell, repeating the process infinitely
While these interactions arent too unfathomably complex, they dont present themselves immediately when looking at a Polluted Delta