Activate Soulfire Grand Master by paying ({2} magic symbol) ({UR} magic symbol) ({UR} magic symbol) , causing you to put the next instant or sorcery card you cast from your hand this turn into your hand as it resolves.
Cast Jeska's Will by paying ({2} magic symbol) ({R} magic symbol) , adding at least seven ({R} magic symbol) and returning it to your hand.
Repeat.
If an opponent has eight or more cards in their hand, this combo nets infinite red mana.
If you control a commander, you may choose both of Jeska's WIll's modes to exile your library.