In a season full of familiar characters, the season pass card looks a little like an old staple card that used to dominate the meta, with a twist. Zombie Scarlet Witch is a card that scales the more you play to her lane by building up a Zombie Horde in another lane. Will Zombie Wanda help the new keyword overrun the meta or will Zombies be dead on arrival?

The Horde Mechanic
This season we're getting our first new keyword since Activate a year ago. Unlike Activate or the other keywords like On Reveal and Ongoing, Horde is unlikely to get new cards each month. The archetype will need to be self-reliant from the start, and Zombie Scarlet Witch is a big part of that. So how exactly does this new mechanic work?
Each time you play a card with an On Reveal with Horde, it will add to your stack of Zombies. If you don't have a Horde on board yet, the first one will create it in another lane. This separate lane detail is an important aspect of the mechanic; don't overlook it. Horde allows you to build power in a lane where you aren't necessarily playing cards and it also gives your deck reach since the Horde can get into hard to access locations, while the random placement of the Horde will magnify the importance of board management.
Comparisons
The obvious first thought many had when they saw Zombie Wanda was old Angela. Once upon a time Angela was a 2/1 that got +2 for each card you played in her location. If you were playing at that time, you know she was one of the most efficient scalers in the game and she rewarded you for what you wanted to be doing anyway, playing cards. The season pass card has similarities, but there are some key differences.
First, the cost. A big part of Angela's power was that you could get her out early and start growing fast. Turn 3 is pretty late and will usually mean you only have 2 or 3 turns to pump your Horde. Second, she adds power to a second location and takes up an extra board spot. This isn't necessarily worse than Angela, indeed it will often be better, but it is a key difference between the two cards. Zombie Wanda doesn't put all your eggs into one basket. How does Zombie Scarlet Witch compare to current scalers and 3-Cost stat sticks?

When you have turns 4, 5, and 6, it should be easy to get upwards of seven activations if you're using cards that can activate and then get out of the way. Making 14+ power Hordes will be surprisingly easy. Of course, this will also depend on your Zombie Scarlet Witch not getting hit with Red Guardian. A Shadow King on your Horde can also undo all of your progress after the fact. The numbers are there, it's a question of if it can be reliably accomplished against an unwilling opponent.
Synergies
Small Footprint
The key to playing more than the expected amount of cards onto Zombie Wanda is a combination of cards that are inexpensive enough and ones that don't occupy space.
Movers
Like the classic decks with Angela, playing a card that can move (or moving one with another card) is an effective way to get the activation count up. This could represent the return of Silk to the meta; I'm less hopeful for Jeff, sadly. This is probably not the primary thing you want to be doing, but it is nice that this version of Scarlet Witch has some synergy with Vision. Good flavor. Props to the chef.
Skills
Skills are the perfect cards to play on ZSW. They don't occupy space and they're generally very cheap. I expect Merlin to be a near auto-inclusion in Horde decks.
Power Scalers
In addition to cards that can efficiently build your Horde, you need cards that can compete for the other lanes while benefitting from your strategy. Cards like Thing, Wolfsbane, and Sage like being played into full lanes late, while Sersi can transform anything small you played into the lane along with Zombie Scarlet Witch herself after she's outlived her usefulness.
Zombie Slayers
Your Zombie Horde and Wanda are both vulnerable to tech, so consider bringing your dog along for protection. Personally, I'm unlikely to play a Horde deck without Cosmo, Juggernaut, Alioth, or some other way to protect my stack of Zombies, especially in the first week when there will be extra Shadow King.
Seeing the Future
The Zombie season is just getting started. While a three card package of Zombie Scarlet Witch, Zombie Giant-Man, and the Hunger (coming later from Sanctum Showdown) is a good enough package to fit into a variety of decks, we've also got Zombie Mr Fantastic (next week) and Zombie Sentry (Grand Arena) coming up later. I’m skeptical of how useful Zombie Sentry will be and incorporating Zombie Mr. Fantastic will mean changing the strategy quite a bit.
Scosco's Day One Zombie Scarlet Witch Decks
Raw Z Power
This deck leans hard into what ZSW does well by rewarding playing into a lane multiple times to grow power and can punish your opponent for playing from behind with NTW and Juggernaut.
Killer AntZ
Your opponent can mess with your Horde all they want. You'll be busy destroying their other cards and growing elsewhere if they rely on that to win.
Zombie Herald
The plan is to get ahead early in one lane and use the Horde and Galactus to compete in the others.
Werewolf VS Zombie
A Werewolf deck with 7 or 8 energy available on turn 6 can be a dangerous thing on its own. The Zombie Horde is just a bonus of concentrated power.
Hammer Slammer
I have to give you at least one outside-the-box concept to explore and both hammers and transformation have a subtle synergy with Zombie Wanda, as well as each other. If you don't get Zombie Giant-Man, replace him with Odin.
Zombie Movie
The exact mix of movers isn't settled, but I do think a move-based ZSW deck is out there. This one includes a mix of movers and disruption, but you could lean further into disruption with Scream or cut Juggernaut or Cannonball for a cheaper mover.
Ultra-Budget ZSW
This is a deck with no series 3 cards that I would definitely feel confident I could use to climb!
Variants
The season pass variant by Ivan Fomin is great, but the Mooncolony and Rian Gonzalez variants are pretty eye-catching too!
Final Thoughts

At 3/2 +2, Scarlet Witch looks like the Zombie card most able to stand on her own, so you should be able to get some mileage out of her whether or not you're planning to get the other Zombies coming later in the month. Zombie Scarlet Witch is unlikely to fall totally flat, but if she were to, Second Dinner would likely swoop in with a quick buff to ensure the season maintains its intended flavor. This card rewards and enables a play style that I've always had a soft spot for, so I'm definitely looking forward to making a big Horde with Zombie Scarlet Witch’s help.