Some ideas and brainstorming from me..
The ShadowBane pack comes and "demands"/asks to suddenly form an alliance with the other packs? I could see them being secretive for the reasons behind suddenly trying to form an alliance when they had been basically absent in the past. We can brainstorm more reasons in the time being. And from there, the packs can decide if they honor the alliance or not. Could imagine most of them would be very skeptical/hesitant. Maybe this creates tension between the packs, with some leaning yes and some leaning no.
But this idea is what I got so far. If at least some packs(or one) agree to it eventually, ties are formed between the shadowbane pack and the pack(s) in agreement. Can be fun forbidden romance there too. Or maybe the ShadowBane pack is just trying to create an ally and tries to convince their ally to turn against the other packs? Creating a massive war? Or maybe they truly want a peaceful alliance and to be in contact with the other packs after being in solitude for so long.
I am also imagining a scene/event when in order to prove themselves as not monstrous, they invite a single representative from each pack as a guest to their territory to see their inner workings for a few days or so. If a pack is interested, whether truly curious or for gathering information/spying, they can send a wolf. And in order to make it fair, the ShadowBane is willing to send a wolf or two into the other pack camps. Just as collateral, or maybe to spy? We can decide.
But this could be an interesting event I thought. The swapping of wolves around can be for spying, can create some new friends/enemies, etc.
Anyway, let me know what you think. These are just ideas for now :)
I like drama, so the more the merrier.