
Spoiler: Tundra (new dual sites)
Source: Frost Mage vs. Lavamancer preorder photos
Tundra - Elite Site
Your {air} and {water} are equal to the highest of the two.
I'd been wondering how they'll design more mana fixing without making it too powerful. The Tundra cycle is cleverly designed with a lot of strengths and weaknesses! One Tundra can give you a ton of affinity, or none at all.
Focusing on weaknesses first, drawing a second copy of Tundra is bad. Drawing Tundra when you're at 1W 1A or 2W 2A is bad. Even at 3W 3A, you'd wish Tundra was any other site. In general you're gonna mulligan towards some amount of both your elements, so topdecking Tundra isn't always great.
When your opening hand includes Tundra, you can mulligan to try to maximize just one of your two elements. It's a little risky though because someone could remove / silence your Tundra. These new duals will lead to interesting mulligan decisions!
I'm thinking the Tundra cycle is all about providing depth for your secondary element. You still want your deckbuilding / mulligan decisions to provide mostly your primary element and a little bit of your secondary element. So the Tundra cycle is a lot like having a double-affinity site in your secondary element, except it's occasionally providing double-affinity in your primary element when you would have been threshold screwed. I suppose we could see more decks going 50/50 with their elements, risky as that is.
The lack of affinities on the Tundra cycle is interesting. The water sites can be used with landmass, which will help certain mud decks. It's a drawback for cards that care about body of water, like Waveshaper. Same for Geomancer and Avatar of Earth, since they're not technically earth sites, and likewise for Avatar of Air.
Worth noting that these duals will be available for mist and lava in November, but not for other element pairs until Q1 2027. (I'm assuming they'll complete the cycle in the next set, because why wouldn't they?) That's about four months of the already dominant element pairs getting additional support, and then everything will get shook up by the new set. I'm optimistic that Frost Mage vs Lavamancer will have interesting mono-element cards in all four elements, breathing fresh air into the meta.