These borderless cards are all either Gearhulks or Gods and are all mythic rare, which makes them even more valuable
Perhaps the best of these is Scavenger Regent, a well-costed board wipe attached to a well-costed creature
For example, if an effect has given Bear Cub, a 2/2 creature, -4/-0 so that it's a -2/2 creature, doubling its power and toughness gives it -2/+2, and it becomes a -4/4 creature
This model became the standard for Magic: The Gathering expansions and began the concept of "block rotation"
Once you've announced that you're casting a spell, players can't take any actions until you've finished doing so
It however is still considered to be in exile and not on the battlefield or your hand, meaning that there are much fewer ways for your opponent to be able to get rid of it before you can cast it