I only have five cards in my hand. Perhaps you are forgetting that I used Swords to Plowshares at the end of your turn. I'll assume that if you have something that can save you from this, you would have kept it and discarded something else (a reasonable assumption, I think). So after you discard a card, I will take all of my floating mana and play Serra Avatar. If you do nothing about this, I will predictably equip it with Lightning Greaves. If you do nothing about this, I will predictably attack you.