The sets feature cards with a Pikachu Jack-o-Lantern pumpkin stamp, giving them an extra thematic flair for the season, and they typically feature a range of particularly spooky Pokmon
Triggered abilities use the words "when," "whenever," or "at." They're often written as "[Trigger condition], [effect]." Some keyword abilities (such as prowess) are triggered abilities and will have "when," "whenever," or "at the beginning of" in their reminder text
The PSA 9 to PSA 10 price gap For many cards, the price jump from PSA 9 to PSA 10 is non-linear
And the graveyard stuff is just part of being a black deck
Feral Ghoul, meanwhile, gets stronger when other creatures you control die, and gives out rad counters to opponents when it goes to the grave