Regulators principles

[Cleretic]

I feel that he could transform, but that without full on access to an unsundered soul like Nidhogg's it would take a toll on him. As physical transformations seem to use a lot of aether. For even not every Ancient was able to physically transform if Hythlodaeus was being truthful and not extremely modest. Though Estinien seems to have kept the ability to use temporary physical clones of himself after said possession and do a huge stardiver/drg lb3. It's been a while since I saw what he exactly does to finish the fight with that experimental ultima weapon in that echo flashback.

Also, the guy can destroy a cannon the size of a building with just a spear, and that's on the LOWER end of his stunts. I don't think he needs the extra juice of a potentially dangerous transformation, guy seems plenty powerful as-is.

[Astralia]

Indeed, Estinien seem powerful enough as is, I just thought of him at the last moment as it seemed believable to me as close enough to Arcadion's fighter to some extent.

But to answer SannaR, isn't it the contrary if we consider Nidhogg's unsundered soul ? Even if with each rejoining, every soul should have taken back a bit of their soul on the shards destroyed (I'm not expert on this part of the lore, sorry for my potential misunderstanding), and Estinien somehow survived Nidhogg's possession and actually has full on access to his soul, or at least his remaining aether lingering in the form of souvenirs/emotions dwelling now in Estinien's aether (that's what I kinda understood actually), but if Nidhogg had been sundered, it should have been easier for Estinien to bear with it and he wouldn't have full on access to his powers but part of it ?

[SannaR]

Indeed, Estinien seem powerful enough as is, I just thought of him at the last moment as it seemed believable to me as close enough to Arcadion's fighter to some extent.

But to answer SannaR, isn't it the contrary if we consider Nidhogg's unsundered soul ? Even if with each rejoining, every soul should have taken back a bit of their soul on the shards destroyed (I'm not expert on this part of the lore, sorry for my potential misunderstanding), and Estinien somehow survived Nidhogg's possession and actually has full on access to his soul, or at least his remaining aether lingering in the form of souvenirs/emotions dwelling now in Estinien's aether (that's what I kinda understood actually), but if Nidhogg had been sundered, it should have been easier for Estinien to bear with it and he wouldn't have full on access to his powers but part of it ?

Well possession in the game seems to take two forms. One that voidsent and ascians do where they take over a person and pretend to be said person. The other is what went on with Estinien. Where it was more of a battle of wills. As both times he gets possessed by Nidhogg Estinien wasn't doing his due diligence of keeping a mental guard up against a few thousand years old unsundered being yapping in your ear every day about how they're going to posesse your ass just like every other person who has held your prestigious position and to then use you to defeat your allies. Dragons in general are different and work different than most other beings on the planet. Midgardsormr and the 1st brood however have and extra detail in that they aren't native to Etheirys as Nidhogg et al were being transported through space as eggs on their dad's back.

We also know that as long as they have an eye of another dragon that they can have a physical body. After we separate Nidhogg's eyes from Estinien it is hinted that a very small part of him was leftover. Now they haven't explained if that was the blood on his lance or if a little soul fusion happened or what exactly. Cause again dragons seem to do everything differently even when they die. So he not only has a smidge of Ratatoskr's blood in him but essence of Nidhogg if only hinted at.

I'm not sure if he does have full access to things he did while having been possessed as some of that is just dragoon crap. I also am not sure if it had been a sundered vs sundered situation if it would have been different as it was more of a battle of wills than the whole "Oh I can't posess you cause your soul is dense" thing that seems to be what determines if you can be "easily" possessed by a voidsent or ascian.