aaronson's potion

As an additional cost to cast this spell remove 3 loyalty counters off of Aaronson, brewer of the arts
Take an extra turn after this one without combat
this cost {b} less for every {2} payed for the {x}. {x} can be {0}
this card can't be in you hand, library, or graveyard if it ever does chose to exile it or put it back in the command zone