The AoE cost may be a bit too steep, but since its an instant spell, the cost is totally justifiable
Miscalculation would either trade fairly evenly, be used on something of low significance simply to get it used before it was dead or get instantly cycled
Sublime is one of the hardest hitting cards cost so reasonably and isn't a high risk card despite being a 4 mana 3 toughness dork as she generally has a strong effect on the game the turn you make her
9 Ursula's Return - Madrigal Magic - Amber/Amethyst Throughout Lorcana's history, Amber/Amethyst has always been the hyper-aggro color combination
Coalition Victory is a fun alternate win condition that was added to the Commander banlist way back in 2007
If youre playing mono white that creates lots of tokens with Clarion Spirit, or a Commander like Emmara, Soul of the Accord or Prava, of the Steel Legion, Halo Fountain will fit in nicely as a mid-to-late game changer