you wont lose any of your hours, or even days, of in-game progress
If youre worried about build time (which is usually about 50 minutes), you can mitigate time anxieties by having a baseline done early (i.e., I know Im playing UB because I have Edgar, Sephiroth, Odin, and Ultimecia, Time Sorceress, but should I splash red for anything?)
We can say the same for descarding spells
With Phenax out (and he will probably stay out most of the time, at least in enchantment form, thanks to the built-in indestructibility), Horseshoe Crab just reads U: Target player mills three cards. That can stack up over time, and many opponents are going to feel pretty silly sending a Swords to Plowshares at your lowly Horseshoe Crab, so they probably just wont
Each 15-card pack contains at least three borderless or extended art cards, and at least five cards included in each pack will be rare quality or higher
The emphasis on the Shire and Biblo Baggins here suggests that Wizards could be prepping a new set of Magic cards inspired by The Hobbit