Yesterday I played a Cassyva with my Arcanyst Abyss deck. Got her to 2 hp in the corner, I was at full (she couldn't answer my Illusionist, I played two Nightshrouds). I had her Kelaino surrounded by a Death Knell and at 2 hp. I have an Aethermaster on board + Loreweavers etc summoned from Knell.
Then she Obliterates.
She goes to 23 and I drop to 11. Oh how the tables turn. But I can still draw more Knells, right? She doesn't have much of a board either, I topdeck an answer to Kelaino. Well over the next 3 turns she chases me across the board and builds up 18 creep spaces. In three turns. With double Crawler and Shadow Nova. Wtf. At the very end she Ghost Azaleas me, despite having worked my way back up to 15 hp.
Never have I seen a board so crazy filled with creep... twice.
Like ten cards left in my deck and I run 3x Death Knell rip