I've seen theories that Kaldheim may have spell/enchantment cards, and Strixhaven by extension spell/artifact ones. Kaldheim probably has the remaining pathways either way.

I figured the new pathways would be an upcoming supplemental set from the "See them very soon" thing. Are there any soon supplemental sets?

The only ones we know so far, I believe, are Commander Legends and Time Spiral Remastered, and neither of those are candidates to my understanding. Supplemental sets in general rarely get DFCs either way. I guess if the die falls on a Pathway Secret Lair?

What are the KHM tribes and mechanics so far? We have

WB angels
UR giants
BG elves
RW dwarves

B berserkers
R dragons

Gain 4 life matters
Vehicles, treasures, equipments, sagas
Changeling

Here's my list of mechanics/themes we've seen so far that we might see more of:

tribal as a major theme
changeling, with some Shapeshifter tribal
Sagas
Angel tribal, WB, subtheme: life gain, life payment
Berserker tribal, BR
Dwarf tribal, RW, subtheme: Equipment, Vehicles, and Treasure
Elf tribal, BG
Giant tribal, UR, subtheme: revealing Giants from your hand

Note that the subthemes are pretty speculative based on one or two cards. Most of this comes from the dump of set and theme booster additional cards, which will not show up in draft boosters.

It looks like we'll probably have 5 main tribes all in enemy colors. UG is unknown, but it might just be shapeshifters? We'll see.

One card references Bersekers (as well as Angels), which could mean one of three things:
1) We're getting ally-color class tribes, one of which is BR berserkers.
2) We're getting a smattering of 5-color Berserker tribal as a sort of viking theme. (This is supported by a 5-color "Vikings" theme booster.)
3) Berserkers aren't a fully-supported tribe, and this card was just a one-off thing.

Headcanon: Niko Aris is two guys in a trenchcoat

Speculation: Dragonkin Berserker, Battle Mammoth, Righteous Valkyrie, The Bloodsky Massacre, Vorinclex, Blessing of Frost, Battle for Bretagard, and Arni Brokenbrow, are all from anonymous randoms claiming to have opened them in Commander Legends packs.

My guess is that all of them are fake. It'd be a strange coincidence if all of the leaked cards were mythic, and I think Mammoth and Blessing of Frost are extra sus because the version of foretell on mammoth just seems like such a bad mechanic. Not just because it doesn't seem fun to play, but because it has so little design space to work with. And as I've said earlier, snow typing is a terrible idea in a set with changeling because it's a supertype so it doesn't work with changeling. I also doubt WotC would give us this many spoilers without even mentioning snow or boast.

Why would they have mentioned snow or boast? Do you assume that the only mechanics in the set are changelings, MDFCs, sagas and foretell? Like half of those barely do anything, I'd be shocked if the viking theme part didn't have some "I love to fight" mechanic associated to it. I feel like snow, boast and runes on top of the suggested themes is a bit much, but Ikoria had a pretty high complexity budget, so comparatively it's not that drastic, Kaldheim might have a breadth of mechanics that are all fairly shallow in complexity.

Changelings didn't synergize with snow in modern masters either, it worked fine there. Changeling also doesn't "work" with evoke, reinforce or clash, it specifically only works with tribal mechanics, which most things aren't. I'm hoping that this is wotc attempting to make a tribal set that is less committal and on-rails than Ixalan, and that the theme-booster cards aren't representative of the set as a whole, but rather designed for the theme decks to give them a stronger tribal cohesion.

I don't care about whatever semi-plausible story the have. Maybe it's fake because the cards are fake, maybe it's fake because the cards have been stolen. I find the whole thing fairly plausible. There's a bunch of artwork that looks consistent with the rest (Toski looks more fake than any of these other cards do). The cards are mechanically kind of quirky, they have these details around them that make them feel like something wotc would make, like they all have this one extra superfluous quirk to them that still feels appropriate with current design conventions. It's hard to describe. They don't look like cards someone would make if they tried to come across as legitimate, like why would you start off with Vorinclex of all things.

I think foretell as spoiled works well as a gameplay mechanic, even if it's not incredibly inspired. Being able to split up your mana cost is a pretty meaningful gameplay decision.

I would actually be more surprised at this point if they're fake because I do think they seem pretty real and the art just too high quality and fitting to Magic. Like there was one fake leak of a new Elesh Norn that was instantly dismissed as fake and yet that's not happening to any of the others. And let's be real: Most of these mechanics take up so little mental space that it's fair to put in a lot. Foretell is Suspendmorph, Changeling and Snow are just markers, MDFCs are more complex especially now that one side at least isn't guaranteed to be a land so it's actually two cards at once, Sagas are a bit complex but this is their third time around, and Boast is just worst Raid (presumably to allow more pushing). And until we know what Runes even are it could be in the same space as Changeling and Snow and just be a marker.

Flavorwise, is Kaldheim based on the Nibelungenlied?

Well we should find out with the stream in 5 hours whether they're real or fake

I can't imagine they won't show us what Foretell actually does, and we'll be able to see if it's the same mechanics in the "leaked" cards.

They really reprinted Snow Basics. Dumb. If there isn't pushed Snow Hate then I expect annoying some too pushed Snow Decks

Not only did they reprint snow basics, but they printed ETB snow duals at common with basic land types.

I don't mind nonbasic snow lands. What I dislike is the pattern of "well I guess I have to replace all my basics with snow basics now if I want to play any snow-related card (or if I might steal one from an opponent)". It vastly restricts the amount of customization in what your lands look like, and makes decks more expensive.

I'm down for more snow basic lands because the art we already have doesn't offer what I'm really looking for.

Well, when I'm wrong I'm wrong.

At the start of gatecrash spoilers I remember saying that Aurelia, Borborygmos, and Enter the Infinite were all fakes

The Niko card makes a shard token but it’s not defined. I had to blow up an ad for Mtg arena but it shows what he does. The card doesn’t interact with the token though.

The normal version of the card has reminder text saying what it is. https://scryfall.com/card/khm/225/niko-aris

It's like a Clue, but it's an enchantment and you scry 1 before drawing.