Archfiend has proven itself worthwhile in Pioneer, where it creates a funny combo with Metamorphic Alteration, as well as in Standard when it was legal, to enable Unholy Annex Chamber
Senseis Divining Top, Scroll Rack or Birthing Pod , you too can play those cards for the small price of one blue and one white - and prevent them from getting the effect on top
In decks that want to be sacrificing things - lets say vampires, devils, demons, goblins and a lot of other Red creature types - this is going to be a huge boon
Unlike Agents Toolkit
Double strike is a powerful keyword
Besides being an enchantment, Fable of the Mirror-Breaker helps this deck so much by generating Treasure tokens, filtering your draws, and mainly copying your big summons like Summon: Knights of Round and Summon: Bahamut