Aferad, Shady Questgiver

Whenever a creature you control completes an Adventure, create a Loot token. (It's an artifact with "Creatures in your party gain +1/+1" and "{t}, {1}, sacrifice this artifact: Level up target creature or
class. Activate only if you control a full party.")

{w/b}{u/b}{b}{b/r}{b/g}: Search your library for a Cleric, a
Wizard, a Rogue, and a Warrior, then reveal them.
Target opponent chooses one. Place that one in your
hand, and the rest in your graveyard.
Then, shuffle your library.