Hey, remember how I said there wasn't any new Low complexity spirits in the game? This is the alternative for those: Aspect cards! Each of the classic four Low-complexity spirits in the game gets a few different cards that change up how exactly that spirit handles. I'll go through them in order of spirit complexity. Seen here is the first of Lightning's aspects, Pandemonium, which transforms their Thundering Destruction innate. Simple enough to understand, it shifts the gameplay focus from raw structure-smashing offense to a stalling game of Fear and Strife. Make sure to put Harbingers of the Lightning to constant use with this aspect, so that Strife can bring in the sweet sweet Dahan counterattack damage.
You don't just replace innates with aspects, you can also transform your special rules. The Wind aspect removes your ability to blitz down invaders at high speed, in exchange for making you a very support-focused spirit for extending that capability, as well as a few more, to others. You still have Lightning's Boon available to speedboost spirits more intensively, including yourself, so you can still do everything at Fast speed if you really want to. Just not, y'know, every turn.
Finally, Lightning's Swift Strike gets a promo aspect that radically changes their functionality. A shift from a focus on card plays to NRG sounds bad, but in practice it's not too bad at all, especially with the freebie elements for major powers. That's really big. You'll want to consider diving for Major powers much sooner with the Immense aspect, maybe even chucking a unique power for it on your first reclaim. Not only does that pay for their own thresholds, it also kicks up your Thundering Destruction innate. Which reminds me: don't mix and match Aspects. It kind of drastically unbalances the spirits, and not in the fun way.
I haven't actually gotten to try out the aspects just yet, but I have seen a few of them played. And River Surges in Sunlight gets some really neat ones. Functionally, this aspect is just welding the Boon of Vigor card to your innates and giving you a choice between whether you prioritize Sun or Water. Y'know how the first thing you should do as River is always "add 2 presence so you get 2 NRG and card plays a turn"? Yeah that's not actually a good idea with the Sunshine aspect. You're better served by getting another power card and improving your NRG, because it turns out that starting with only 3 cards is really bad for your tempo. Like the Immense aspect above, you'll want to go for Major powers here, seeing as you'll eventually be able to virtually double your NRG income with this innate.
This one looks really fun. Being able to slip'n'slide the Dahan all along your lands is handy, as is getting free Sacred Sites wherever there's a bunch of Dahan (and River's Bounty makes that easier than ever). Sure you lose the easy Sacred Sites just for having presence in Wetlands, but being able to freely move the Dahan around more than makes up for it. You'll want to look for Defend effects more often than usual, though, because that meager Defend 1 won't do a whole lot on its own.
While most of the aspects increase the spirit's complexity, that's not universal. Vital Strength of the Earth's Resilience aspect is about as complex as normal. A common discovery when playing Strength is that the Defend 3 is good, but not good enough once the Invaders really start building up, and if you get overrun, it takes a LOT of work to get back on your feet. So being able to keep the Invaders from adding blight for ridiculous lengths of time sounds fun. That said, you'll need to be a LOT better about carefully managing the Dahan, and it gets harder to work with them without that easy Defend. I don't think I'd see myself playing this aspect very often, unfortunately.
This one, on the other hand, I want to play on my next game. You still lose the innate Defend 3 and that sucks, but getting boosts to damage AND better card play and gain is an extremely attractive package for Vital Strength of the Earth. The Might aspect is just raw beefy offense in its simplest form, and I am VERY here for it.
Finally, Shadows Flicker Like Flame, generally considered one of the weaker spirits of the base game. The Reach aspect just lets you turn off Range on one of your things per turn, which can be handy given its inclusivity on where it can be used (hello turn 1 I'm on the opposite board's coast in a 6 player game). This also means you've got a little more wiggle room to stockpile NRG without needing to nickel-and-dime yourself on Shadows of the Dahan. But by that same token, you lose the ability to use that rangehax more than once a turn, and sometimes that's a very big saving grace.
I'm just gonna say it: Glimpse of the Shadowed Void is weaksauce. Purely meant as a consolation prize for if you or other spirits fail to capitalize on the free Strife on your presence. But hey, a little bit of extra Fear and Strife is always nice, and the bonus Fear does make Concealing Shadows less of a suicide play for the Madness aspect.
This one is very, very good. We've discussed with other spirits why being able to freely move your presence around is so handy, and Shadows Flicker Like Flame is no exception for being able to utilize this. You can dodge the worst of Concealing Shadows as above, set up new sacred sites for Darkness Swallows the Unwary, get out of a land during Ravage only to bounce back in with a range 0 hammerpower... sky's the limit, really.
The Foreboding aspect gives up the ability to flexibly dunk on Dahan-bearing lands in favor of pointing at one land and going "you are Die". Given the focus on Air for this one, this works best if you're speeding on card plays, so you'll get more wiggle room to decide which of your two innates you want to focus on (or, ideally, get the perfect card draws to trip both at once on the same land).