He has a historical knowledge of games that I've seen rivaled by only a few people (Richard and Skaff Elias, by the way, have actually taught a college class on the history of games) and a wonderful intuitive sense of how game design works
R Rare Ghost Gardna X DARK Level 4 [ WarriorEffect ] ATK 0 DEF 1900 When a face-up monster you control is selected as an attack target, you can change the target to this card
draw 1 card and show it, then if it is a "Fluffal" monster, you can Special Summon 1 monster from your hand
The result was "TDK" (Thundurus, Deoxys, Kyurem)a deck archetype so fast and consistent it warped the format around it
A lot of big creatures now though have caveats like cast triggers or if you cast it triggers, to make cheating them out less good, but even so huge creatures just getting dumped out is fairly scary
Target player puts the top three cards of their library into their graveyard