Had a bit of a strange idea for a crow/magpie commander. I originally wanted it to be combat with fliers = discard, but I think this works a bit better.
Arvoc, Treasure Thief 2UB
Legendary Creature - Bird
Whenever three or more creatures with flying you control deal combat damage, create a Treasure token.
As long as you control three or more artifacts or have three or more artifacts in your graveyard, creatures with flying you control get +1/+1.
I know that the Black doesn't show here except in the graveyard, but I am adamant that for flavor reasons, any bird depicted as a corvid should be both Blue and Black, in the same way that Owls are depicted as being Blue and White.
I kind of like the fact that it has a near permanent anthem effect if the conditions are met, but that might be too strong, even with the hoops you have to jump through to turn it on. The mana cost might have to go up by 1 (because it is so wordy), but if that's the case, I think an extra point of toughness would make that worth it.
I like the design, but I feel like the anthem effect is overused for flying matters commanders. If you’re worried that the anthem is too strong, you can remove black. Mono blue has had artifact graveyard interactions before, Emry, Lurker of the Loch, and that kinda limits self mill recursion. If you’d rather keep black, you could go with
“Whenever three or more creatures with flying you control deal combat damage to a player, you may sacrifice a non-token artifact. If you do, gain control of target artifact that player controls of lesser mana value. Otherwise, create a treasure token.”
Plus, the flavor of crows stealing things is pretty fun.