Well ... not the way you would probably like to.
You can support her original plan: Complete ritual, kill every and any non-druid within the grove and lead it as new First Shadow Druid.
You cant "join" forces with shadowdruids, since they ... i would say, have no use for you.
But if you with Shadowdruids to win anyway, even if you have no gain from it ... there are two ways that i know about:
- You can kill Halsin (or simply let him die as he battle with Goblins) ... and dont expose Kagha ...
Im not entirely sure, since its quite some time i did this ... but i believe that if you kill Goblin leaders, you can also save Tieflings, who will leave ... next day in the morning, Grove gate will be overgrown by huge thorny plants and the area will be filled with posion.
(There is still way to get inside if you Distant-Mistystep trough that path behind a Waterfall ... but Druids will attack you on sight.)
- You can kill Zevlor ... and tell that to Kagha.
No matter what you do next, after single Long Rest, Grove will be sealed (thorny veins and poison) and any Tiefling that you didnt kill so far will be dead inside ... druids are again hostile on sight.
> If you save Halsin, he tells you that he no longer cares if you kill Goblin leaders, since Grove is doomed anyway ... this can be quite interesting outcome imho, especialy if Goblin leaders have some role in the future story.
> If you side with Goblins, Minthara will be pissed that you screwed her plan and attack you ... this is actualy great way to burn all your bridges and end up completely alone.
