[K Peculier]

Alright first of all. I recommend you go on a deep lore dive reading spree first as  there are bunch of stuff in here that is just made up lore. I will tackle your requests one by one and explain though I won't lore dump everything in here save links to some pages.

USEFUL PAGES TO READ: https://neus-projects.net/wiki/index.php/Vampire https://sl2.fandom.com/wiki/Vampire https://sl2.fandom.com/wiki/Heaven's_Contention
https://sl2.fandom.com/wiki/The_Enlightenment https://neus-projects.net/wiki/index.php/Gods https://neus-projects.net/sl2lore.txt

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"The first is that Kaizer is a very old vampire and knows how to survive as one. I would like him to be about 600 years old, but I'd love some feedback on what would work well for the timeline I have in mind."

1. The timeline of recorded civilization starts from 0 within the in-game time records. Which is why vampires at 300+ years old have to apply since you'd literally be a vampire from the start of civilization.

The second is that Kaizer has been perpetrating a tradition where he pretends to be different people at different times through history by using dark magic to slightly alter his facial features (more on that subject in the lore section). I'd like to apply for his particular brand of ancient dark magic to be a legit thing that can allow him to alter exclusively his general facial features. This would be minor and not extend to other people or other parts of his body, only allowing him to hide his identity, provided he also changes the rest of his appearance through disguise and other means. The power requires him to be freshly empowered by having drank the blood of a person and takes about 15 minutes to perform, uninterrupted in the dark.

2. Dark magic isn't actually the right 'domain' for illusions meant to trick the eyes and senses. At most you'd disfigure yourself by smashing your face with whatever dark magic you have. Ancient dark magic is also far too convenient and grand for virtually no drawback. The most powerful 'dark' magics available to everyone would be Void Magic which runs the risk of void poisoning and in exchange for more unique powers of obscuring/healing.

If you want to disguise yourself temporarily you'll have to use normal illusion magics or the good old full mask/helmet. Physically disfiguring yourself outside of using the void, you'll eventually heal and revert back to your most 'prime' condition as a vampire.

"The third is that a historical event occured 550 years ago after a war between chaturanga and sigrogana, known as the Mignight Murders, where 31 war veterans were killed in a brutal manner during their sleep, over the course of 40 years."

3. Chaturanga and Sigrogana haven't even existed as proper warfaring nations yet and even then I'd have to say no because an ancient Vampire has much better things to scheme and do than murder a bunch of soldiers in their sleep. If you want to play a newly turned antagonistic vampire who does this in the current timeline, you're completely free to attempt so however.

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If your goal is to make a fun and interesting villain. I HEAVILY SUGGEST starting at a more younger vampire age. Living around the era where Sun's Ichor was active is probably a much better point and then building your story and reasons for being/doing what you do versus getting some unexplainable power from some otherwordly source.

You will find your story and character much, much more rewarding to play if you started small and worked your way to infamy/power vs already having it all. Once you figure out a general plan that you want to go through, you can contact an Eventmin to set up a stage for you to start antagonistic actions (Necromancy, Thralls, Etc).

tldr; This request is a no for now until you rework many things or start a new one with a different concept.