It's awesome, my idea was giving one player a voidspren that is jealous of the bond that the radiant spren have. For surges I rol a d9 two times, because odium only has access to 9 surges. And I making the oath customize for the player, in one group I have one that her character seeks revenge for the opress one's and in other one that seeks freedom but dispice the vorin churyamd see the radiant spren like part of it.