Since I just brought up running more lands, I want to talk about the addition of utility lands to the mana base since the deck no longer runs many cards that care about swamps
His last ability helps finish the game, but it probably wont be used much until then unless you can put pressure on the table
You could combine it with cards like Bristlebane Battler to make more saprolings (or even better, to leech from an opponent that has that card and kill it later by doubling its counters)
Many counterfeits either block light too strongly or let it through unevenly
This works with all permanent types, and means that if you sacrifice a treasure token, you not only get the mana from the token itself, but Korvold gets stronger - and you draw a card, too
He does not like you at all, and if you play any sort of a spell, you are about to take some serious hurt