Some of the most popular commanders for spell slinging decks are Mizzix of the Izmagnus, a card that can greatly reduce the costs of instants and sorceries, and Veyran, Voice of Duality, a card that doubles any abilities that trigger from casting an instant or sorcery
Well go over the different variants of the Mega Charizard X ex cards
Red isn't quite as efficient at blowing things up outright, but it has much more flexibility
There are 46 Avatar The Last Airbender pack themes altogether, so you can get different character, scene, and elemental combinations without needing to draft or hunt down singles
Conclusion I hope this has been helpful in giving you not only an overall understanding of the Dimir Demons deck, but also the way in which we build and think about decks like this