Welcome a new Affinity lord in Modern -- Karn, Scion of Urza. This planeswalker is going to be busted in all artifact-based decks. It is currently the most expensive card in the entire Dominaria expansion, and it will only get pricier.
But Modern is not the only option, as Karn will be just as good in Standard. Decks with Tezzeret and Hidden Stockpile will snatch this planeswalker the moment it appears on shelves. So be prepared for some token infestations in this meta.
All this makes Karn, Scion of Urza one of the most investment-friendly cards from Dominaria.