You can grow it as large as you want, and it generates treasure tokens when it dies
Exchange that card with the top card of your library., so you basically just end up losing the game and probably a Swamp, but if you are able to cast a Darkpact you get to essentially trade your opponent a Swamp for whatever they anted - pretty dirty and cheesy, especially if they flip over a spicy rare
Supporter cards are played like Item cards, but you can play only one Supporter card each turn
While sacrifice sources are extremely important in these sorts of decks, this cards biggest strength is its ability to exile cards from graveyards (Im looking at you, Uro)
Competitive viability can temporarily boost prices, but once a card rotates out of standard formats or strategies evolve, those prices drop