Festival of Embers on my battlefield prevented me from casting cards from my hand, as well as cards in my Adventure zone. Additionally, after one of my creatures was exiled with it after dying, (Taii Wakeen), it still triggered the next turn when I killed a creature and was then animated with my opponent's Virtue of Persistence. Somehow the game seemed to think it was exiled, in my graveyard, and on the battlefield at the same time. Lost me a standard event but not a super big deal.