When doing this, you have to be careful to avoid being offputting or wangsty. Proper angst is one thing, but a character whose whole existence boils down to "I'll live forever so what do you matter? " or "Who wants to live forever? " is really, really annoying.
And also: Ignore anyone telling you to be original. Cliches become cliche because they work. Knave's own character looks like the knock-off spawn of a couple generations worth of Nyarlathotep worshippers from the Lovecraft Mythos with a few generic Signs of Villainy scattered in to give a moral perspective. Visla is basically a stock subversion of a Mary Sue waif spellcaster. I refuse to comment on my own characters, but I'm sure anyone can pick out about ninety atrocious stereotypes in any one of them.
Originality is irrelevant. An enjoyable story is all that matters. If you find a formula that works, whether it's older than dirt or fresh as newly cut grass, go with it.