Cast Harmless Offering by paying ({2} magic symbol) ({R} magic symbol) , giving Necropotence to an opponent.
The opponent skips their draw step due to Necropotence.
The opponent is unable to cast any cards put into their hand from Necropotence due to Teferi only allowing them to cast spells at any time they cast a sorcery.
At the beginning of each end step, Sire of Insanity triggers, causing all players to discard their hands.