While each card has an icon in the top left corner to define if it's the front or the back (such as Innistrad-based sets using a Sun and a Moon, or Ixalan having a compass and a mountain), the front face is always the one with the mana cost
A neat trivia note is that these five represent half of the cards in all of Magic that use the character string any number of times. We also have new double-faced cards, enough to warrant their own section
(Some abilities can also target unexerted cards.) But not using them has less of a direct benefit - you dont need to defend your life points, as in MTG or Yu-Gi-Oh!, so leaving cards upright is typically only worthwhile if theyre likely to be challenged by your opponent and you need them for a future turn
Vampires are my jam, along with Merfolk
Remember, we are working with averages, so this cost is factored into the 65% of decks that do not play the planeswalker
It made up 31% of the meta for Modern at the time of the ban, as it was used in both Dimir control decks and Rakdos Aggro decks