It's not a bad choice. While it does add corruption points, the player will still be able to decide whether or not they embark on a darker path if they accumulate enough of these points. So feel free to kill and spare who you choose because there isn't a clear right or wrong answer to these problems.
Corruption just means that the connection with Death grows stronger. It's not meant as being evil. If anything, the MC makes a case for why killing Oruth could be the 'good' choice instead.
Hey, thanks for the suggestions. I do plan on refining parts of the story in v0.9, so this gives me a few ideas of where to start.
Regarding my intentions for the story in this update:
Annestria and Ellania (the elven sisters) are probably what you are looking for.
I can't commit to anything incest related due to the ToS of a certain platform, but both Ann and Ell will be available to the MC as sexual/romantic options, including as part of a harem.