Presenting a WindfallWindfall once a turn, Jace's ArchivistJace's Archivist will cheat the best creature you have in your hand into play for four mana with HashatonHashaton, and will give up to seven creatures +2/+0 and the ability to OphidianOphidian with Captain HowlerCaptain Howler
She has extensive knowledge of zonotssinkholes that lead to Ravnica's oceansthat is invaluable in recovering submerged evidence
It is an incredibly efficient mana accelerator that is seeing play as a four-of in Standard, Modern, Pioneer, Legacy, and Commander
The flashback in particular makes it attractive for a midrange style deck, where the reanimation is something of a B plan
For a simple activation cost of (1)(R), you can cheat a creature from your hand onto the battlefield with haste, sacrificing it at the end of the turn
No matter what type of player you were or what you cared about, you had to enter each new set through the same booster as every other player