Mana Cost At the right of the top line is what we call the mana cost
We've got a guide to all the MTG Arena codes that are still working to get free boosters from earlier sets.
Rest in Peace A lot more relevant these days than it used to be, Rest in Peace (RIP) hates on Snapcaster Mage, Tasigur, the Golden Fang (or Ladyboy, the Golden Wang as I've heard him called), and Become Immense, as well as the odd graveyard deck like Gifts Tron
A three mana 3/2 with Toxic 1 is already probably playable, so the fact it spits out a Mite when it dies is sweet
Playing a second Rishkar, Peema Renegade is actually way more useful than most legendary creatures would be
Hemlock Vial is a black egg, which we dont get very often