Whenever a player casts their second spell each turn, you lose 1 life and create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Spells that were cast before Lotho, Corrupt Shirriff count. If Lotho, Corrupt Shirriff was the first spell you cast this turn, the next spell you cast this turn is your second spell.