Mono mono mono mono spirit
Here is my first take on four only spirit decks that should work together. I have to say that it was crazy difficult to make that list trying to cover every aspect of the game, but i think it's a good start.
Fist of all - Heroes
I wanted to inculde all ranged and sentinel characters available so Legolas, Lanwyn, Beregond and Théoden. Then I took a shortcut including Seastan's deck - Caldara 2.0 (modifying it slightly to get rid of non-spirit cards) and two obvious positions (at least for me) - Glorfindel and Éowyn. Éowyn gonna be so important allowing to discard those Elven-light and providing huge questing as a single character. But finally we got to our last heroes and since I still wasn't sure about defending capabillities of those decks I decided to include Frodo Baggins, Merry on the other hand allowed me to make secrecy deck and Eleanor landed last with her great ability and low threat.
I decided to take advantage of discarding mechanics that comes with spirit, fisrt of all we got swarm of Zigil Miner with addition of Imladris Stargazer and Elven-light. That combination of cards give us card draw and resource acceleration, also works great for Caldara deck. Also, there are several heroes that can recycle those Elven-light so they should be able to keep coming over nad over again.
Then we have things that boost our main protector of the game - Beregond. Desperate Defense, Blood of Númenor boosts his defence and with Unexpected Courage and Miruvor keep him up for additional defending. I tried to take advatage of Renewed Friendship just because it's a very versatile card that I do not see that often. I think the biggest problem gonna be the archery damage, my only response was to put high HP allies in every deck, but with no healing that's for sure gonna be a soft spot for those decks.
Since we are in A Test of Will territory there are few classic cards along with Eleanor that can make our day easier. In every deck there is also threat reduction in form of either Elrond's Counsel or The Galadhrim's Greeting, there are couple more cards to keep threat low and they have other uses too since I tried to keep everything versitale.
I really think that this list is a good start but need a lot more polishing to be great, it's a nice chalenge to make four decks that works together. Please share your thaughts, I would really appreciate a feedback from more experienced players. Cheers!