Option One: Anafenza, the Foremost Anafenza is a hideously effective Dredge hate card that also annoys Arclight Phoenixes and comes strapped to a body big enough to survive Lightning Bolt
Feed the Swarm One of the biggest shifts in Magics color pie over the last few years has been blacks newfound ability to handle enchantments, and Feed the Swarm remains the standard-bearer for this utility
If you are a tournament player, knowing your Power 9 is also important because these cards are restricted in Vintage tournaments and banned in Legacy and Commander (the single exception being Timetwister in Commander format)
It was first printed on sorceries and instants, but also appeared in the Warhammer 40k Commander decks on three permanents, including Sister Repentia
Existing Coded Power Levels There are a number of existing power levels within Commander beyond cEDH
The fact that I could spend money on cards and then get money back out of them afterwards was really enticing to me, especially at the time