Activate only as a sorcery." The number of creatures you control is determined as the activated ability resolves
Ikoria s mutate mechanic also has plenty of rules headaches associated with it
Here we learn of the origins of the Brothers War, a years-long battle between brothers Urza and Mishra, who harnessed the power of the Mightstone and the Meekstone to lead mechanized armies against one another
If Phyrexian Fleshgorger is no longer on the battlefield at the time the ward ability resolves, use the power it had the last time it was on the battlefield to determine how much life that player must pay (though if Phyrexian Fleshgorger was the only target, the spell has no legal targets anymore and hence it would not resolve even if they pay the life)
Gale's proficiency as a spellcaster is well-represented through his card due to his ability, which allows you to cast an instant or sorcery from the graveyard if you've already cast one from your hand
I suck at math, but luckily Frank Karsten covered this very problem in an excellent article that I highly recommend reading