If Kaalia attacks an opponent, the creature enters attacking that player even if Kaalia is somehow attacking a different player or planeswalker as its triggered ability resolves
So, aside from being powerful in its own right, Vivi Ornitier has a lot of support that you can use to create a very effective spellslinger deck
I think the neat statline may have caused people to overvalue this slightly
Decks like Krenko, Mob BossKrenko, Mob Boss, Isshin, Two Heavens as OneIsshin, Two Heavens as One, and Etali, Primal StormEtali, Primal Storm would absolutely love this card, as it enables them to do "their thing" the turn they come down
You then get one lore for each one point of damage removed through Baymax
Jhoira, Weatherlight Captain Though Jhoira, Weatherlight Captain references historic cards generally, it almost always ends up being an artifact deck that combines Jhoiras incredible card draw with 0-cost artifacts like Lotus Petal, Jeweled Amulet, and Mox Amber to generate immense bursts of card advantage
