Bounty: Sleepy Sovka ask you to go a turn without casting spells, a feat best suited to control or Tovolar, Dire Overlord // Tovolar, the Midnight Scourge decks
She ends them decisively
The third time youre tempted, any creature that blocks your Ring-bearer must be sacrificed at the end of combat
This allows collectors and pack openers to have beautiful, high-value cards to chase after while enabling players to be able to utilize the more practical, albeit less rare versions of the same card
Besides these physical implications, it should be considered that someone (the players or a judge) will need to control the validity of the cards - which may prove difficult with some of the above points
Being able to tap down something like an Ulamog, the Ceaseless Hunger or Hazoret the Fervent is a big plus, even if it does cost us two (effectively three) mana to do so