okay, so i thought that said WHAT does your oc value above all else, not WHO, so i already typed out a response for what, so you're getting both!
above all else, elias values.. personal freedom. the ability to choose what you want from your own life. they've been in situations before where that has been taken from them, and that was awful for them. and they hold this for other people as well, even if someone else chooses something awful, elias could never bring themself to take away someone's right to choose. it has lead them into many sticky and horrible situations before, but they still won't shake it.
pennitha values memories and histories. she writes a lot, because when her lover was murdered, all she had of her was a few scant photos and letter snippets. when she dies, she wants her knowledge to be passed on, for others to know she existed.
letters values... well, letters. a similar, but different reason to pennitha. it's how we communicate, how we share our knowledge and stories, and really it collects forms of communication. it seeks to understand others. this also leads to it prying secrets out from unwilling victims, but such is the price for knowing.
for elias it would be their partners, chief among them Harper Faraday! Harper has been there for them for a long time, taking care of them on bad days, but never seeing them as anything less than a whole person.
pennitha values her dead love most of all, but in her grief, she's started seeking out and mourning another
letters does not value any specific person, and in fact it has trouble connecting those its corresponded with to when it meets them in person, there's a bit of a disconnect. over time this can be mitigated, but not ever fully solved.