9 mana is achievable for green decks, and T&N is just a reliable way to shut the door on a game if you get to cast both modes
Running a five-color deck, however, means you have to carefully calculate the mana costs across all of your cards and balance your lands and other mana-generators accordingly
The main commander is Kardur, Doomscourge, a demon who forces all your opponents to attack a player other than you
Where it actually matters is the matchup: against a go-wide aggro table you grind them out with blockers and lifegain, and against slower value decks you simply have more gas than they do
That is not to say you have to play the most expensive cards to succeed, just the best ones for your deck
Illustrated by Jason Chan Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Legal Brawl Not Legal Legacy Legal Comp