Although they might not be as into memorizing the pokedex as he is, many of the kids seem to have an official card or two in their hands at all times
When you do, up to that many target creatures each get -2/-2 until end of turn
You might have missed her reveal yesterday - Nissa, Ascended Animist is an interesting case, as if you pay the full seven mana for her, she's much stronger, able to create bigger tokens, destroy more artifacts and enchantments, and even pump up your whole board right away
And once you're a black-red deck with Heartless Summoning, you really can't do anything better than cast more Demons anyway
Since theyre all from disparate worlds and games, they each do pretty distinctive things with little common ground, but nonetheless its possible to build a fun themed deck around cramming in a bunch of final bosses