Imagine a dark-side path choice where you side with the shadow druids, cow the other druids, and your real 'boss fight' for the end of the arc, just when it seems like the grove is going to be a walk-over now, is a furious and righteously indignant Halsin who, his patience exhausted waiting for the right moment, has left his goblin containment (because literaly nothing was stopping him leaving at any time, other than his desire to gather intel) and returned now to reclaim the grove on his own - Because He Can Do So and it takes your whole party plus your shadow-druid colleagues to overpower him + the remaining druids that take arms to support him. That would be so satisfying for an evil-side arc.
Theoreticaly it sounds good ...
It would be perfect for a cinematic ending ...
But practicaly it sounds incredibly boring gamedesign. :-/
Do you realize that your party would be just those lowly suckers that will permanently miss, almost dying after single strike from Halsin and even if they finaly hit, they will give him so "huge damage" he would probably not even notice?
Its the same problem that was mentioned when GM4Him suggested boosting Halsin's level, and adding friendly NPCs to help you first time ...
I mean look ... if you make Halsin level 15 as is suggested here ... he would have acces to level 8 spells ...
To take one example:
https://www.dndbeyond.com/spells/sunburstCombat started, Halsin casted Sunburst ... your whole party is dead (if i count corectly most of them even if they succed in saving throw).
Fun, right? ... right?
But even if he would have all spellslots abowe level 2 depleted ...
He would still be ridiculously tough. :-/
I dont even know what forms he would be able to take on such levels, but i dare to presume it would be something much more powerfull that his curent bear.
I know that GM4Him suggested that other NPCs can help us take him down, and they should be boosted too, to ballance out his power ... but it just dont seem fun to me ...
Example again: (all numbers are chosen just for explanation purposes)
Combat started ... you give him 1d8 (Cantrip), astarion will give him 1d8+2d6+DexMod (dunno, ranged Sneak attack), laezel will give him 2d6+1d4 (ever burning blade), Shadowheart will do nothing bcs you really do want to save your spellslots for healing in this fight.
Then Kagha came to scene, she is level 13 ... since she was in the Grove this whole time, she have no reason to have spellslots depleted ... so she casts 7th level Firestorm ... and gives him 7d10 damage ...
(Wich if i count corectly means that she just single handedly give Halsin aproximately double damage than your own party ... is that really fun? :-/ Woulnt be easier to just hide somewhere in the corner and skip through that fight, since you dont really do anything anyway?
)
Then another NPC step up and do the same to diminish your value even futher.
-_-
(Besides i dont really see any reason to give him such level in the frist place if he would be "weakened" and his spellslots used, since then he is simply the same Halsin as we have now, with just adjusted statistics, as we have now
)
Not to even mention that with all those characters it would take ages for you to at least get your turn. :-/
I mean, agro whole Goblin camp can be quite tedious, not bcs its anyhow hard fight ... but bcs it takes quite long before you can do something ... but in that scenario you at least reduce your enemies, so your turn gets faster and faster ... here they would be friendly.
