Many legendary cards have higher costs to compensate for their stronger abilities, so Kethis giving you a flat one generic mana less cost for them helps get you in the game faster
Cauldron of Souls is an amazing Artifact that lets you recur Creatures...especially the few that are over the three mana value threshold
Squandered Resources Cards with the highest ceilings often have the lowest floors, leading to designs like Squandered Resources
Gravecrawler does still support the other cards Bloodghast supports quite nicely
On the side of good, we got Ethan's Ho-Oh ex, Cynthia's Garchomp ex, Steven's Metagross ex, and Marnie's Grimmsnarl ex, and to oppose them, we got Team Rocket's Mewtwo ex, Team Rocket's Moltres ex, Team Rocket's Crobat ex, Team Rocket's Nidoking ex, and Team Rocket's Persian ex
It's important to us to make cool alternate versions of every rare and mythic rarethey're all someone's favoriteso rares and mythic rares that don't appear in any of the above treatments will appear in extended art