Regarding the First's Warriors of Light/Warriors of Darkness and the role quests:
First, it looks like we've got some name retcons going on, or alternatively their names on the First were different: Arbert is now Ardbert, Blaenherz is now Branden, Lamimi is now Lamitt, J'rhoomale is now Renda-Rae (the biggest change, as far as I can tell), and Naillebert is now Nyalbert (I think - didn't write that one down in time, and the journal doesn't record his original name in the first quest, which is all I have access to right now).
Relatedly, their Sin Eater names are Greek: Blaenherz/Branden's name is Dikaiosyne, meaning 'righteousness' or 'justice'; Naillebert/Nyalbert is Phronesis, 'wisdom' or 'intelligence' in the sense of practical knowledge/intelligence (as opposed to 'sophia' which is wisdom in the more abstract sense of knowing the good); Lamimi/Lamitt is Sophrosyne, 'temperance' or 'self-control'; and J'rhoomale/Renda-Rae is Andreia, literally 'masculine spirit' but generally translated as 'courage' or 'valor.' They're all playing off of the title of the Four Cardinal Virtues that they're collectively bestowed, which originally derives from Plato but is often referred to in Christian theology and ethics, tying back to the vaguely Judeo-Christian theming of the Sin Eaters as a whole.
Looks like my Greek skills are finally coming in handy, though it makes it difficult to figure out how they want us to pronounce the ones ending with -syne, since English often pronounces those as 'sign' while the original Greek pronounces it as 'sue-neigh'.