1) Shudderwock. It costs 9.
2.) Murmuring Elemental. It costs 2. That means you have to make an 11 mana play.
3.) In order to make this possible, you must play Fire Plume Harbinger while the Murmuring Elemental is in your hand, or you can get either the Shudderwock or the Murmuring Elemental at reduced cost using Far Sight.
4.) You have to have played two Lifedrinkers at some point in the game.
If you have satisfied the above conditions, Shudderwock will deal 12 damage to your opponent. That is unlikely to be enough to kill them.
That means you also need to have played Saronite Chain Gang and Grumble at some point in the game, so Shudderwock can send copies of himself back to your hand, hopefully setting up a lethal play no sooner than turn 11.
If you manage to Grumble when Lifedrinker is on the board or use a Murmuring elemental to double down a Lifedrinker's battlecry, you can increase the incoming damage.
But in order to set this up, you have to spend multiple turns doing low tempo plays. I think people are reacting very negatively to the long animation Shudderwock sets off, which kind of feels like it's doing an end-zone dance on your face. But this is a win condition that requires a lot of setup, and in order to get all the pieces, this deck has to invest a lot of resources in cycling through cards. It's not clear at all that it's actually more consistent than something like the old Aviana/Kun/Malygos Druid OTKs or the Exodia Quest Mage. When I've pulled it off, I've been near fatigue. This win condition is much slower than something like pre-nerf quest rogue.
What I am actually seeing a lot of are very aggressive Hunter and Paladin decks. Baku lets hunter put a tremendous amount of pressure on with its hero power, and if it gets in a couple of hits with Huffer or a Bearshark, or a kill command, it can end the game long before a Shudderwock combo.
My guess is, when people stop experimenting with the Jimmy cards and start trying to climb, they're going to do it with paladin and hunter decks and Shudder Shaman is going to be blown off the ladder.