Exiled Grist, the Hunger Tide with Vivien, Champion of the Wilds' -2 ability. Was unable to cast Grist, no permanents or cards in graveyards indicated an interaction like "can't cast from other than hands" effects. Pretty sure it was a bug that treated Grist as a noncreature despite its static ability making him a creature as long as he's not on the battlefield. Wish I had screenshots to add.