this adds a great deal of tension during play, as you wont know what your opponent has seeded the Spell/Trap zone of the field with until its revealed
Graded Population Report: Starly #75 Visualize the distrbution of grades in the chart
2 Urza, Lord High Artificer Artifacts Bow To Him One of the most powerful single commanders in Magic, Urza, Lord High Artificer is an incredible commander to play, creating an immense amount of mana while also helping you dig through your deck for free spells
Considering that the Rampant Growth effect is far from irrelevant, we can't go too high
In Commander, its not hard to make this do a lot of work for you, and its going to be adopted very quickly into a wide range of decks
The main line that she specifically enables is the Firemind's Foresight into a one mana draw spell (like Brainstorm or Whispers of the Muse)/Lightning Bolt, Reset/Reality Spasm/Dramatic Reversal and Reiterate