Defensive cards like Seal of Doom force your opponents to make a decision about how much they want to potentially lose in an attack
Creature-based counters like this have been beloved at the kitchen table ever since Mystic Snake was printed way back in Apocalypse
The mana value is about right for this effect, though a bit intense on the blue for it
What makes its random ability even funnier is that it is an 0/2, meaning it is likely to eventually kill itself
I had it pinned as the best common at the start, and I still feel the same about it
It's very strong in multiplayer since you are more likely to be running at least one opponent with Green ramp and two-drop ramp spells like Rampant Growth and Farseek are getting added to ramp brews in Commander over conventional ramp like Cultivate and Kodama's Reach, so on the turn you have three mana, one player casting a two mana ramp spell with an extra land is pretty likely, and if not, then someone probably cast Explore spells or dropped an Exploration and an extra land or two
