For those totally new to Pokemon cards, or trading card games in general, expansions usually add lots of new cards to collect, and can even feature new rules and changes
(1) Special Summon 1 Sacred Beast monster from your hand or GY in Defense Position, then, if you control 2 or more Sacred Beast monsters whose original Level is 10, you can negate the effects of 1 face-up card your opponent controls, and if you do, destroy it
As another grindy deck looking to simply outvalue opponents over time, these GB lists are perfectly positioned for that kind of card
No, its not from an Un-set or Secret Lair, its from Ikoria: Lair of Behemoths
If it's the player's only thopter, it withdraws to their hand and creates a small fleet in its place