7 mana is really expensive for a commander, however, and 6 isnt much better from Phylath, so Id recommend playing a lot of ramp and card draw if you elect to build decks around these legendary creatures
Alania, Divergent Storm I love that Alania, Divergent Storm pays you off for going all-in on Otter Spellslinger and tempts you to use it as your Izzet commander
(Or vary in their power enough that the user is uncertain what effect the card will produce during any one use.) The ability has cemented in black and is also used in red and artifacts quite a bit
Funeral Room // Awakening Hall Funeral Room is a bad Bastion of Remembrance, and Awakening Hall is a nerfed Rise of the Dark Realms
Allowing a player to consistently return creatures from their graveyard to the battlefield with little cost is an absurdly strong ability
And then Sapphire characters that can boost each other's stats and work well with item cards