Bloomburrow

Sorcery

Look at twice X cards from the top of your library. Put X cards from among them into your hand and the rest into your graveyard. You lose X life.

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This is the actual decklist that I own.
Draft the Commanders first from a special pool (in the sideboard) with 4 packs of 10 or 12.
Each commander has partner. If you want to use one of the companions, you can do that as well if you abide by the companion rules and color identity rules. For Umori specifically, you may still have creatures as your commanders as long as the rest of the deck follows its companion rules.
I suggest choosing your commanders (and sometimes a companion) before you've drafted from the main pool. 
Each player automatically gets a command tower and an arcane signet.
Before drafting, players can decide if they want to draft 60 card commander decks or full-sized 100 card decks.
Draft 4 packs of 14 for 60 card decks and 6 or 7 packs of 14 for 100 card decks.
Color Identity does not matter when it comes to lands.
Draft Archetypes:
Reanimator
Cast spell, get value
Freecasting
Theft
Copying spells
Value for targeting your own creatures

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Rules Text

Card Facts

Legality

Rulings

Every version

Decks using this card