Second, it provides a Rat deck that wants to proactively win the game in a way that strays from the traditional style of big go-wide combat or aristocrats
Moltres , Zapdos and Articuno are basically the same card with different types, and I think thats why the three of them can be analyzed together (they basically have the same ability, attack, HP and retreat cost)
Due to the nature of his exile ability providing him with +1/+1 buffs, Umbris gets quite high power/toughness consistently, causing you to have a lot of free building space to slot support and pet cards, or cards that are nightmares or horrors by accident that just happen to work very well with his exile effect
While this card is incredibly valuable, it's not the most valuable Eeveelution card in the set
There will be games where it feels far better than that grade implies, but there will be just as many where its significantly worse The Rat not being able to block here is obviously a big deal, but if you can pick off an X/1 with this while adding something to your board thats nottoo bad