Weakness and Resistance are based on two primary components: The type of move the Active Pokmon performing the attack is using
When working in conjunction with spells such as Fury Charm and Timecrafting that are capable of removing time counters, one would be hard-pressed to find more efficient means of playing massive creatures within the Izzet color identity
For Marshal to get its full value, you need a creature to die before playing it
If youd prefer to be a little more aggressive, Omnath, Locus of the Roil is the commander for you
(The same is true for card types that don't appear in most games, like plane or scheme.) You can't choose a subtype, such as creature types like Spider or Hero, artifact types like Treasure or Food, or enchantment types like Aura
This gives you a somewhat aggressive aura based go-wide deck that also controls the board politically which is really cool