My first April Fool's joke in a video game was a little over a decade ago, when we replaced a jet in a mobile game I worked on with a model of a horse
Brisela, Voice of Nightmares is made when Gisela, the Broken Blade and Bruna, the Fading Light are just on the battlefield together, while Hanweir, the Writhing Township is made through an activated ability that melds Hanweir Battlements and Hanweir Garrison together
Also, this aura offers a huge buff to a creature, if you're interested in the mechanics, of course, and not just in how very cool the artwork is
Meanwhile, Lilianas +1 has each player discard, prevent your opponent from interacting or gaining card advantage
Notably, Korvold will benefit from any Magic card type being sacrificed, not just Treasures, so the deck can also use sacrifice-related cards like Sakura-Tribe Elder