Hell yea it is
I've been brewing Breya. All I have to say is holy shit.
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What doesn't she do? First off, her colors are perfect. She's artifact-based so green's only strength is irrelevant due to the amount of mana rocks you're going to be running. She has a nontapping ability, which is also a sac engine, which is also a win condition, damage, and sustainability. Did I mention it's nontapping, so you can use it multiple times? She's a combo just waiting to happen.
My favorite combo with her so far:
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Combined with Breya's ability, you can produce infinite colorless and infinite thopters.... which then results in infinite board control, life, and damage. I say that's pretty deece. Redundancy can include Krark-Clan Ironworks instead of Ashnod's Altar, and Eldrazi Displacer (not an artifact) instead of Ashnod's Altar. You're also in WUBR so you have a million different ways to tutor this combo.
I'm still deciding on the rest of the shell for her. I can either go with a goodstuff.dec list and run the Esper sphinx package + some Daretti and goblin welder fun. I can do an artifact-based Stax control deck, which allows me to sacrifice away engines that I find annoying. Or should I try something else?