Thaumatic Compass / Spires of Orazca Thaumatic Compass might be deemed too slow for a more optimized deck, but Im a huge believer that Commander decks dont need to be optimized
Before I dive into the main list, however, I want to tackle three small honorable mentions: Planewide Disaster This card is the only phenomenon on this list
They are part of one of the cheapest competitive decks in the Pioneer format, in this case Mono-Blue Spirits, which costs just a bit over $100 to complete
1 red mana is just so inexpensive, and while discarding your hand sounds like a horrible thing to do, if the table dies because your 10 goblins got +4/+4, it's insane
When original Ravnica was released in 2005, it got solidified much more strongly into specific naming conventions of those two-colour pairs we have since called Guilds
Four mana is pushing it for aggro, but reducing major spells down to 3 mana can be huge