Plot

Yesss, let the conflict brew!

Idea vomit time. The small group of cats aren't the first of their kind to visit the area, had a scout previously find the area then who has also return with the current group of invaders who's mission is to infiltrate and retrieve information on the clans. Spying. Their ultimate goal is to put a war into motion between the clans so that the natives wipe themselves out. In order to inflitrait the native groups to acomplish their goal, one of their tactics includes having she-cats who appear to be helpless or in need of protection. Possibly even some who are going to have kits. Those who aren't already with kit would make a point of finding a mate quickly within the clan, baring half blood kits as to farther incorperating themselves into native life and win over the clan's trust. With the added mouths to feed the group will convince Fogclan that they need more territory, that they deserve more territory, why should things be split up so equally when clearly Fogclan is the strongest clan, and by far more deserving of the most territory. If the other clans don't comply peacefully then, well what choice do they have but to start war with them? Fogclan needs that land, for the sake of it's future kits. If there's a dry summer that would give even more reason considering Fogclan only has one stream in their territory which would probably dry up, leaving them with only the rivers that seperate the territories. Pray will be scareser. Giving them a reason to try and take the marsh from Willowclan.

The whole infiltration process could take either 1-2 years. Depending on if we want to wait for halfblood kits to be born and how quickly the group can get Fogclan's trust and convince them to expand their borders and start a war. 

The cats will have entered the plato through a cave near the Starfalls which eventally opens up to a pass through the mountains winding down to the valley below. It's about a two moon journey from pass to the group's current base of opperations, the group it's self is large and war loving, having no problems with murder. Possibly lead by a large cat who is given almost god-like statis, believed to be a descendant of a mountain lion. Doesn't really matter though we're not gonna see more of them aside from the group that has entered the plato. The cats who were chosen for this mission have in some way a desire to prove themselves and a certain blood lust quality, though and cunning enough to keep it under wraps. The mission leader will be especially capable of their task. All members are highly trained, none too particularly young. Most of them have done this before as it is a common practice in their group, even if they're not after land or resources it's a source of honor, the more cats you kill and the more cultures you  take part in destroying the higher ranked you are within the group.

Time line of events kinda sorta. For about a moon or so they will have entered the territory, leaving scraps to make their presence known. Once it is they allow themselves to be captured and infiltrate Fogclan. Gain their trust which could take 2-4 moons if we want to. It'll be leaf fall by then so either they'll start encouraging war for the sake of their kits, to gain more territory to last through the winter and keep fogclan fed, which will have the war begining in Leafbare. OR if Fogclan desides to wait til spring and start the war then, the war could go on all year until next leaf bare, giving a solid couple of moons of war to weaken all of the clans. Depending on how things work out the group of cats will send someone back to their leader either at the end of their first or second leaf fall before the pass is blocked by snow (2 month journey) and they will return in the spring with the full might of the group's army to completely take over the plato and wipe out the now war weakened and winter weary clans. BUT this won't happen because either a) the other clans will convince Fogclan the group of cats isn't what they seem (meh) b) their true colours will be revealed somehow through either their actions or an overheard conversation (just before winter when there's still a chance a scout can escape and lead the army back to the plato) or c) one of the younger members of the group betrays them, telling their true intentions to Fogclan, feeling guilty about what they're doing, not wanting to take part in it anymore.

Once their intentions become clear, Fogclan will have to try and stop any of them from escaping through the cave and the pass. If even one manages to escape there could be a lil adventure of a few selected cats who get to go after them and bring them back, the other clans sending a representative or two, not trusting Fogclan's warriors to do it on their own considering how badly they'd screwed up inviting these invaders into their land in the first place. OR the clans simply block off the cave completely, filling it in with rocks and bramble and anything else they can find, making it impossible to enter. Therefore trapping the invaders in the territory. Breeze and Willowclan will want to outright kill them for the trouble they've caused, but seeing as some of them are mothers of Fogclan kits, Fogclan will be torn on what to do with them. Some will stay with Fogclan, specifically though who mother kits. The majority of the group though will attempt to flee. Being unable to leave the plato they claim the Star pool and Star falls as their territory seeing as it wasn't claimed before. This then has the clans in an uproar, leading to small interval of time in which the medicine cats cannot travel to the starpool freely. Gatherings will be held on what to do with the invaders who can no longer leave the territory. There will be thoughs who demand their death, and blame Fogclan for all that has happened, others will insist they cannot simply murder an entire group of cats who have no where else to go. Even Fogclan won't want to take them all back. There will be disputes over the territory Fogclan claimed during the time of war, willowclan may demand a part of Fogclan territory insisting that since it was their fault, they should pay for what they've done and that they should also give up a portion of their territory to house the invaders, the dead forest maybe. Leaving Fogclan worse off than it started and far more tense, angry at the other clans. More potential for future wars and border skirmishes. 

So the clans will have to deal with tention from Fogclan and the now rouge group of cats living in Fogclan's side of the dead forest. And the constant fear of the invaders group outside of the plato finding another way in, another cave or pass that the clans don't know about as of yet. But probably won't happen since the group's leader sends out mulitiple infiltration forces all the time so if one group were to go missing it would go unoticed. The clans don't know that though, so the now rouge group will use that fact as farther reason to keep themselves alive, threatening if they are found dead their group's army will destroy the clans for it.

okay I think that was everything in my head.