Reyhan+Akiri suggest a deck around the "Modular" mechanic. Sacrificing Modular creatures one after the other with a Doubling Season effect out can generate a gigantic creature.
• Creatures that use and/or give counters
• Sacrifice effects
I'm considering cutting Akiri (and thus Red and White) from the deck, and replacing with Slurrk, All-Ingesting or Nadier, Agent of the Duskenel.
Or I could use Sakashima of a Thousand Faces (which would add Blue), and then I could add some copy effects to have multiple Reyhans.
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Click here for my EDH Commander decks