This could be through blacks removal, reds direct damage, or blues bounces and counterspells
The deck isn't quite as good at protecting Electrumite, but in exchange, your draws are more consistent and you can gas right through interruption
One card of any rarity is traditional foil
#1 Sheoldred, the Apocalypse Sheoldred, the Apocalypse Dominaria United, Mythic Surpassing Liliana of the Veil as the most expensive card in Dominaria United is Sheoldred, the Apocalypse
They can also get quite messy, though, to the point of replacing Having a fun time with Having a massive rules-comprehending headache, or with Having a bit of a bitter argument with other players. But fear not
Generaider Boss Stage is central, as it lets you Special Summon when your opponent adds a card from the Deck to their hand