Viane was Khaos's human companion.
- According to Roshule, Viane was killed by the very sword that he gave her. At first, one would assume an enemy soldier stole the sword from her and killed her with it, but then Khaos reveals that Shylphiel's original counterpart was killed by her own comrades, which lines up better with Roshule's account.
- Khaos's companion took a fatal hit for him, which doesn't seem necessary because of how hard Ancestors are to kill. On the other hand, Viane's sword is the Infinity -1 Sword of the game, which she probably thought was too deadly even for him.
- Khaos kept the sword and one of Roshule's spears in his dimension, implying these are Tragic Keepsakes to remember her by.
- During Reviel's fight with Hypnosis, Roshule thought of Viane just by witnessing his Ancestor powers, suggesting that Viane has some connection with Khaos.
- Shylphiel is quite skilled with swordplay for a Badass Normal, which suggests she may have inherited Viane's experience with swords.
- Shylphiel shows some reluctance in going into Algiz with Luna. If she really has Viane's appearance, running into Roshule would be extremely awkward.
- Viane's mother is named "Millphiel", which sounds a lot like "Shylphiel".
- Both Shylphiel and Millphiel have blue hair, only Shylphiel's are clearer.
- It is not uncommon in fictions to have a character who came back from death with paler hair than in their 'previous life'
Reviel's ability to Cast from Experience Points is an in-universe skill and not just him using brute force.Even after Luna joins the party and becomes a vampire lord, there's never an option to spend her experience and MP to destroy obstacles like with Reviel, which means only Reviel can do it. It's possible that Reviel was either born with this technique (like with Ristill's creation ability) or developed it himself after dealing with Ristill's puzzles for so many centuries.
The barrier weakened Ristill too due to her being the same species as Reviel.Khaos created the barrier as a way to weaken Reviel and set up a puzzle in the final dungeon, but Ristill never took this opportunity to try to kill her rival, even though her use of the Dark Chains Curse shows she has no problem with trying to weaken Reviel through her own means. It's possible she couldn't make a serious attempt on Reviel's life because she was weakened to a similar degree. However, this is unlikely because Khaos is an ancestor too. Alternatively, he could have set up the barrier as a way to buy Ristill time to complete her Maxwell research and even the playing field between the two.
The potential of Laplace's Demon is limited in some way.Khaos introduces it as a barrier of Combat Clairvoyance, allowing him predict any move, thoughts or actions of his opponents, allowing him to dodge attacks accordingly. After a moment of silence, Reviel responds that he'll just have to use 'unavoidable attacks', which make Khaos scoff, unsurprisingly.However, should the player decide to use the various Limit Breaks, they will discover that those actually do hit, albeit without any chance of critical, I see two explanations to it:
- It's a simple oversight. It's possible. And after all nothing is said if you actually do that.
- Laplace's Demon and/or Khaos have limits. The implication seems to be that the Limit Breaks are so powerful and fast, that when used, Khaos, is indeed informed, but cannot dodge them nor protect himself fully. The lack of criticals could be interpreted as him making the best of a bad situation: using the foresight gained to minimize the "unavoidable attacks" in way it won't injure him as much as it should. It's also a bit more reinforced by the scene where Ristill joins up and states that the barrier can 'merely predict'. In conclusion, Laplace's Demon gives foresight, and it's up to the user to use it well, even in front of unavoidable attacks.