In the modern collecting game, its all about Rainbow Rares (a rainbow recolouring of some Pokmon and trainers), Gold Rares (a select number of blindingly sparkly bits of cardboard) and the big daddy: alternate art
Rotating formats are fun because they keep changing, but in Eternal formats you can continue ruining your opponent's day with your favorite Mill Crabs long after they've left Standard no need for drastic gameplay changes here
Treasures are a real thing, and a valid strategy
Keep in mind a planeswalkers static abilities will still be in effect, so a card like Sorin, Vengeful Bloodlord will still grant lifelink to your creatures and planeswalkers while detained
A few personal favorites are Raised by Giants to make him a 10/10 or Folk Hero to give you a card advantage and access to White
Unmatched by any McDonalds set that came afterwards imho