For one red and X mana, you get X 1/1 Rats that can't block, and then you give all of your creatures haste so they can all attack at once
As for what it does, thats hard to tell because it literally doesnt tell you
Not much is known yet about these sets, but it's likely that more will be revealed closer to their releases
Zidane Tribal (Ragavan, Nimble Pilferer) Rating: 8/10 Oh boy, are we about to see another format dominated by Ragavan, Nimble Pilferer
(2021-03-19) If a nonbasic land has an ability that causes it to enter the battlefield tapped, it will lose that ability before it can apply
Once you exile a card that meets the discover requirement, you can choose to cast it or put it into your hand, but unless you cant put cards into your hand or cant cast the spell for some reason as the ability is resolving, the card wont remain exiled