It seems well put together and the capture tokens turning into fear actions starting an action snowball is interesting, but it seems to have one major problem that plagues all birdsong scoring factions (in this case turning in capture tokens in birdsong to get points NEXT TURN), that you can be easily disrupted, but if you aren't, everyone has a big problem on their hands. My main gripe: it takes 3 turns to get any fear tokens used. Turn 1 - get capture tokens, move them to pyre. Turn 2 - burn them at the pyre. Turn 3 - spend FINALLY. 2 turns I can understand, but 3 turns before you can use your main mechanic seems a little much. Now, once you spend those fear tokens you get A LOT of vp, making this a very snowball faction, and if stopped before you get snowballing, it will be very hard for you with some well timed policing to remove capture tokens.
It's unclear how you put warriors on capture tokens. Is it one capture token per battle? Per warrior? Your choice? If you already have a capture token, can you add more warriors to it? Why would anyone choose anything but single warriors for capture tokens to get as many fear actions as physically possible?
Overall, a good mechanic with no major problems other than the length of time it takes to use fear tokens. Probably not extremely overpowered, just medium to strong