If a "Dinomist" monster you control battles, your opponent cannot activate cards or effects until the end of the Damage Step
They don't have to attack the same player, planeswalker, or battle that Calamity is attacking, nor do they have to attack the same player, planeswalker, or battle as each other
While Pikachu ex can fire off powerful Circle Circuit attacks for just , Mewtwo exs Psydrive attack costs a whopping and requires you to discard each time you attack with it
RL Max Burst 20+ You may discard any amount of basic [R] Energy or any amount of basic [L] Energy from this Pokmon
You could consider a few more mill cards like Court of Cunning or Psychic Corrosion to ensure your opponents actually have enough cards in their graveyard to exile but again: Umbris tends to grow large on his own
Nothing like that feeling of coming out with a W