Say via Delina, Wild Mage, who puts nonlegendary copies of the demon onto the battlefield already tapped and attacking
Example: If you attacked and your opponent's creatures are strong, ending your turn is like saying, "I'm done for now, let's see what you do." Instant Spells Saving instant spells for your opponent's turn lets you react
Either way, I'm still a sucker for this sort of 90's Goth Comic Book kind of monster design, like the enemies from American Mcgee's Alice and whatnot
3 Roaring Moon: Prismatic Evolutions (Master Ball Pattern) $21.42 Mastering The Look Master Ball patterns rose to prominence thanks to their inclusion in the Japanese version of Scarlet & Violet: 151 and they're back in Prismatic Evolutions
Play something like Crawling Chorus, get in some poison, and then go wide for the win