If youve ever watched a drink get set down next to a Commander pod, you already know why people do this
For a 5-color Commander deck, the optimal mana base will probably require 10x fetch lands (like Marsh Flats), 10x shock lands (like Godless Shrine), 10x bond lands (Bountiful Promenade), a handful of the best 5-color lands, and a few Triomes (like Jetmir's Garden)
Going straight from 3 mana to 6 the next turn after you play a land lets you rocket out some terrifying beaters like Hellkite Tyrant and Ancient Copper dragon quite early, and you can run blacks cheap graveyard tutoring like Buried Alive or Entomb to gain easy access to a variety of threats
10 Double-sided Tokens
While this creature is an absolute powerhouse in more niche decks like Odric, Lunarch Marshal, you can bet that any Eldrazi-based or mono-green deck can power this creature out in no time
It means that Soulless Jailer dies to things like Fatal Push and Solitude, which is bad, but it also means you can find it with cards like Collected Company and Chord of Calling, which is good