I can't fit all of this within the character limit so I will continue it in the replies.
In the Final Fantasy XIV Live Letter on February 18th, 2021, Yoshida answered a question about Venat clarifying that during the battle where the player fights Hydaelyn, she expends the aether of her soul, causing it to be destroyed and the primal to fade, which is why she says that not even her soul will remain as she’s dying. I’ve seen several people interpret this as Venat being unable to return to the Lifestream and simply becoming nonexistent forever; however, I have my doubts as to this particular interpretation. I’ll be frank and say that I really hate the idea of Venat being doomed to oblivion, unable to even rest in peace. It’s deeply upsetting to me and feels like a kick in the face after everything she’s done for the player, especially considering the game’s habit of fridging certain female characters; however, I also feel like I have in-game evidence to support the conclusion I’ve come to, and would like to explain why.
My position is that Venat did actually return to the aetherial sea, and that her soul being gone doesn’t contradict this. As we know, souls consist of aether, which is basically Final Fantasy XIV’s version of matter or energy. While aether may be expended to fuel certain actions, it doesn’t seem to be entirely destroyed in the process. There have been multiple instances of characters having their aether absorbed, drained, or scattered only for their spirits to show up later. In the fight against Nabriales, Moenbryda sacrifices her aether to power the blade of aether that would kill him. Despite this, when the player ventures into the aetherial sea during Endwalker, a manifestation of her soul or memories still appears. When Minfilia arrives on the First to stop the Flood of Light from destroying Norvrandt, she absorbs the souls of the Warriors of Darkness except for Ardbert in order to gain enough power to do so, leaving his shade to wander alone for a century. Despite this, at the end of the Shadowbringers main scenario after Ardbert has fused with the player character, he can be seen reuniting with his friends’ spirits. Minfilia allows herself to be absorbed into Ryne to give her the power of the Oracle of Light, but despite this, Hydaelyn is still able to bring her soul back to the First.