MUD gets a card that is easy to Workshop out, disables the Time Vault combo, and is extremely powerful as fodder for Goblin Welder and Kuldotha Forgemaster
All of these are good, just get them all
So if you really want to know what promos are Pauper legal, you have to find a list of all common Magic Online promos then MANUALLY LOOK UP EACH CARD to see if it has other online printings (in which case it isn't legal), unless one of those other printings is at Common (in which case it is legal)
Withering Torment fills in this sorely needed gap with a three-mana instant spell that destroys either a creature or an enchantment
I wanted to see a cool double-faced card of him transforming into one of his overpowered bosses, but alas, the designers didnt do him justice
I really like how this card rewards aggressive lines of play, and how The Nuka-Cola Challenges trigger encourages diversifying your attacks on multiple opponents