I don't know how I feel about the whole descendant/reincarnation shebang with the Divine Warriors in canon so I reworked it a la Yu-Gi-Oh to include a system for partial reincarnations.
So, after you die your life force is sent on but sometimes pieces of it fall off as they travel to the afterlife and drop back into the mortal plane. This happens to pretty much all living things, sometimes including wyverns.
Sometimes the pieces land in plants and animals and collect the experiences of those things to pull into their soul and whatever they move onto next. Sometimes they land in a living person. When that person has a kid, the stray soul piece is passed on to the kid and gets mixed into the kid's own natural soul as they grow, making them, ba ba da ba, a partial reincarnation! This also works if the soul piece drops into an infant or a kid young enough.
For very rare for a soul to be born or develop with completely new parts. The energy is recycled in the ether while the person part of the soul goes on to the afterlife, but the majority of new souls are made up of parts that fall off in transit, which can sometimes lead to strange magicks or prophetic visions depending on what got mixed in. People who get flakes of wyvern souls get the gift of prophecy 99% of the time, though most of the time it's garbled by the disparity between the minds of humanoids and the minds of wyverns.
Enki has flakes of wyvern in him, and he can't understand most of them which frustrates him to no end. Zane has what he perceives as prophetic visions for wyvern-unrelated reasons. Kul'zak ended up with a soul made mostly out of plants and goats, which makes him very in tune with nature and traveling the world and it's also why he feels like kindred souls with goats (his sacred animal).
When it comes to relics, descendency doesn't matter as much as having the core part of someone's soul reincarnate in you, though sometimes it'll turn out by sheer coincidence that your descendant IS the best partial reincarnation for the job, like with Travis and Enki. Sometimes the pieces of soul end up completely disjointed and the relic just latches onto whoever is most similar in core aspects to the previous holder of the relic, like Shad and whoever ends up with his relic.
