Okay this is a fantastic concept and pun. Having the twig start in an ennemy homeland in very flavorful, and to be honest everything about this faction is a flavor win.
The twig powers are all bonkers, so I see your ennemy being tempted to use them. As waritten however, I believe in birdsong you could chosse X=50, draw 50 cards and stay at 0VP because you can't go in the negatives. I assume this is not intentional ? Can you use all 3 twig abilities during daylight ? It might be a bit broken for let's say woodland alliance to be able to recruit 4 guys in one action.
If you are the player with the least VP, do you keep the twig ? If that's the case I think you want to be sandbagging and intentionaly stay behind on points in the early turns until you are maxed out one warriors. You could also prevent yourself from discarding each turn to end up with more than 10 cards in hand and a myriad of action.
Devoured warriors filling the track is a really good concept, even if the price of detroying an altar might be a bit too harsh.
Overall, I love it :)