The gold cards are the Ultra Prism Secret rares
"Perpetually" allows players to permanently "change the characteristics of a cardno matter where it goes afterwards." The effect of Davriel's Withering will not leave a creature, even if it dies and returns to the board at a later stage
The story is engaging but never overwhelming, perfect for players who like their lore blend in rather than be dumped on them
But it's also not really overpowered at all - in fact, it's probably the best thing that could've happened to the game's casually competitive scene
You already have a few effects like Elesh Norn, Mother of Machiness in this deck, so you can replace this pricey card with an inexpensive tutor to help find one of the others
If any Phyrexian ever dies, it lets you proliferate, making them grow even larger