Again, Cult of absolute threatens *everyone*
Technically true ... on the other hand, it dont seems like *everyone* knows about the cult.
On the contrary, it seems like *nobody* knows about them.

So, you want to unite forces that despite your way of living against common enemy they never met and who never threatened them directly. O_o
[irony] Yeah, that would totally work well. [/irony]
Kahga literally asks for your help in-game already.
Eh ... did we play the same game?
Bcs in mine, she dont asks for anything ... she meerely points out that Tieflings would use your help. O_o
This isnt *I* need you to do something for *me* scenario ...
This is when *I* do what *Im* doing, *they* would need you ... so if you are interested, go talk to them.
Heling them with the Tieflings or the druids would be doing them a service no matter how you slice it.
Well, it saves them some trouble ... that much is true.
But dont overstate it, we meerely make it easier for them, hardly anything more.
And it would make a heck of a lot more sense for them to not fling back the helping hand offered them, particularly when that hand might belong to another druid, who they already have a demonstrated interest in spreading their ideology to.
I cant agree with this, they are not looking for convertites ...
If they would, they would simply teach Tieflings the way of Druidism, converting them in the process ...
You are talking about helping them ... but if you would really want to help them, you wouldnt expose Kagha, they would never know, and the Grove would be sealed ... if you interfere, you are creating unnecessary problems in the process ... true, you can state afterwards that you dont really care, or want to help, but at that point, you allready screwed it.
Why exactly would they risk that you screw something else in the future?

Or they could ...not... Y'know, like you could ally with them in BG I+II.
Oh you played as future Mind Flayer in BG I or II? No? Didnt think so ...
So how exactly is that relevant?
Their leader in BG III was literally a party member in the first game. This is just fishing for excuses to explain why this weird half-finished quest is the way it is in the game.
Different game, different time, different stakes, different situation, and most importantly entirely different Game Master.

This is just fishing for excuses to fullfill some weird fanfiction of yours. :-/
The reason they want to do it is to take over the grove, doing it via the rite or expediated via the player's hand is just different means to the same end.
Well, if you mean by it that both lead to sealing the Grove and severing any, and i mean ANY, connection to outside world, then yes ...
The rite isn't something all shadow druids live under, it was just a means to an end-a risky one too as explained in the game.
Besides, the rite being performed in one grove doesn't protect them everywhere. Again, the cult is a threat everywhere in the region.
Maybe they do now ...
I mean, we only explored quite small area *somewhere in the wilderness around Chionthar* ... how can we say what is happening elsewhere?
Be honest ... lets imagine you are leader of Shadow Druids for a second, yes?
If you would have a several places, that you would need to protect ... and lets say that you would know about threat that may cause them harm ... and you would have ritual, that you would believe to keep them all safe ...
What would you do?
A) Send them all instructions to do the ritual ... therefore keep them safe and protected against every and any outside influence or problems ...
B) Send your whole cult into open war, potentialy against rest of the world, with uncertain end, bcs
"some random dude in middle of nowhere, interfered with one of your agents asignment, but in the end that dude decided to take your side, after he threatened everything" ...
And again ... be honest.