This card reminds me of a card from the recent New Capenna Commander product called Spellbinding Soprano, but it feels like a much more powerful and more repeatable version of that card with the addition of myriad to replace encore and the ability to flash in sorcery spells
These are all in the past, though
It becomes a finisher if you can keep the crown, dishing out incredibly amounts of damage for a mono-blue card
Grimgrin enters the battlefield tapped and can't untap on its own, but at the cost of sacrificing another creature, Grimgrin untaps and gets a +1/+1 counter
The one way to break it's cruve-based drawback is to have your turn two play be a ramp spell (like Growth Spiral, Incubation Druid, Paradise Druid) which in turn allows you to play a four-drop on turn three
Don't use this unless you are casting a Templar Knight since we don't want to give up our deck