This effect is simply not one the Arena developers want in the format, with the Flare cycle from Modern Horizons 3 and the envoke Elementals from Modern Horizons 2 all being pre-banned in the format
Literally so big that she had to be imprisoned inside a moon, shes of a massive scale that puts her in striking range of Genju
Murderous Rider is just that plus the option to maybe have a creature later on
All were established decks prior to the release of Magic: The Gathering FINAL FANTASY, but the sheer popularity of Izzet Prowess and Azorius Omniscience has exceeded even the expectations of Pro Tour veterans and coverage insiders
While plenty other high mana, high impact creatures are available, building a Commander deck with the aim of melding Brisela is such a fun concept, and shouldn't cost as much as it currently does
One possibility is to play Intuition, which covers one card in your hand, graveyard, and the third one which you can play