Rock You Like a Hurricane

This is a wind herald combo deck, you win by getting all 4 wind heralds in play, ideally with a Mirror Image in your void and ending the turn. If you have Mirror Image you'll be able to copy the Avatar of Wind over and over, dealing 5 damage each time until they're dead (or your board is full of Avatars, but they'd need at least 70 life to survive that). If you don't have Mirror Image, Avatar of Wind is still crazy strong on it's own but you might just lose to removal. If you can't get the combo off, you can also just beat them down with a bunch of fliers and card advantage.

If you use Haunting Scream on a Herald the combo still works - South Wind Herald's ability activates before the Unit is sacrificed to Scream. Scream can also hit Skyward Seer, a lot of times you want to use it on her after combat so you can fetch a combo piece.

The removal package is flexible, but Extract is really nice in the deck and I don't think I'd go under 2. Annihilate has been pretty alright, but I might switch one or two of them for more Deathstrike or even Feeding Time depending on the meta.

Black-Sky Harbinger is here because you can get it with Seer and it's one of the best stabilizers in the game. This deck isn't really aggro enough to end the game before it's relevant, and a lot of times we just need to survive a couple more turns to combo off. Harbinger is crazy good at helping you survive a couple more turns so it fits. It kind of messes up Whispering Wind as you're not guaranteed to get North-Wind Herald from discarding a 5-drop, but it's definitely worth it.

Mirror Image is the real MVP of this deck - it's part of the Exodia combo and it really greases the wheels. You can use it with Haunting Scream and Gorgon for massive draw, you can use it with Seer to fetch more combo pieces (you can even use it with Seer and Scream to fetch two combo pieces). It gives you a slow infinite combo with West-Wind Herald, and you can use it on Harbinger for even more stabilization. I only run 3 because you generally don't want it in your opener, but you do want to see one pretty much every game and with all the draw and deck thinning we have you usually do.