Zanarkand, Ancient Metropolis - always a banger during Distant Worlds, having a fail case of this being a 6/6+ creature in the late game if drawn late is something that could work out in its favor
Blues other tutors such as Mystical Tutor, Tezzeret the Seeker and the mage-cycle are all great but Spellseeker takes the slot here
Since theyre created tokens and not copies of another card, they have a mana value of 0 and can be removed immediately by cards like Ratchet Bomb
The weird duals (River of Tears, Nimbus Maze) and filter lands are also considered full sources for each of their colors
The decks for Commander are also different, requiring exactly 100 cards with no duplicates (other than lands) as opposed to MTGs standard ruleset which requires at least 60
It handles beaters and utility dorks, big things and small things