Last March of the Ents
Humans are trying to cut down the trees to build more of their settlement. Orcs want to hide in the forest and ambush anyone else that comes by, but their stench stunts the growth of the forest and ultimately spells its doom. Finally, elves want to live in the forest as well, but their capricious nature makes them a poor choice of neighbour, equally prone to burning down parts of the forest in fits of rage and caring for it.
Each round a certain number of each race assault the forest and the Ents must protect against them. Thanks to all of the clearing that has already been suffered by the land surrounding their forest, the Ents are able to see them coming from a distance. The Ents, however, are slow and so their range is limited once they have to start protecting against the attackers. In return, the Ents are invulnerable. They will not fall until the last remnants of their forest is destroyed.
Now, whether those who made it into the forest leave, I haven't yet determined. It makes sense for the humans to leave with the lumber they seek so greedily. Perhaps those capricious elves that light fires also find their end in that tragedy. Finally, the orc population may attack any leftover elves in the forest, with the remaining orcs staying in the forest until they find more creatures to attack.
Once these effects have been resolved, then the forest can grow, remembering that trees grow really slowly. Then the next round begins and with each subsequent round, the number of attackers increase. The game would need to be very finely tuned so that it is just possible to win each round, where winning is not being completely overrun that turn and losing a large chunk of the forest. The idea is that the game is supposed to be difficult, as darkness falls over the land, protecting what is important to the Ents becomes more and more distressing. But, if they win, then they have completed their duty in protecting their forest and in time they know it will bloom again.
Pilgrimage
As they progress, characters will collect items that can help them. If a militiaman survives his/her first combat, then s/he gets a helmet to protect them in future combat. But if any pilgrim dies, their goods are distributed amongst the caravan and your new pilgrim starts with nothing. The idea here is that if (really, when) your pilgrim dies, the player simply draws new background and agenda cards and becomes one of the other pilgrims in the caravan. If they draw the same background card (i.e. militia), then they get the first item straightaway, collected from the corpse of the previous pilgrim.
One of the event cards in the event deck will be "Reach the Stronghold". The game ends when that card is drawn. The player who has the fewest dead pilgrims in front of them is the winner. Once again, the game is meant to be difficult and death will happen regularly. Nice events will be few and far between, if they occur at all on your pilgrimage.