Notes & Combos
This is a good list for Umi Control atm. The deck doesn't really struggle to win from the meta. The only thing preventing you from getting winstreaks with this deck is getting a really bad hand, which isn't often, or facing an insane board like whatever adamancipator players put down after their 25 min combo.
Thunder Vassal is so good in this deck that i feel like everyone should run at the very least 1 and the extra deck will only get used by Pot of Extravagance so feel free to use more Dogmatika hate.
Top Secret Packs used

The token staying on your opponent's field is actually a benefit to you, because it means they can no longer use Imperm on you, and can no longer put a non-Water on the field without getting rid of the token first themselves. By using Token Collector, you defeat the point of Mithra in the first place.