ok yes so i really like that pretty much all of the ancients we met were so strongly tied into some conception of justice - either idiosyncratic (venat) or societal (elidibus) but arguably everyone had views that fell somewhere in the middle. of course you have the shades of amaurot having a typical agora debate on the matter of trying to help their overseas neighbors during their time of need and what would be the greater justice & overall better deed, to set the tone, but more generally:
venat and the sundering come as the most obvious example: she's literally making her own principles, after which she will render her own justice, even though the cost is great - alienation from her peers and the people she loved so well, the burden of guilt, unending vigil; the notion there may not be any greater justice beyond what we each do and believe in, too, maybe
elidibus is a close second, considering ever since his first appearance in ARR, he introduced himself as the neutral, equitable, incorruptible emissary, arbiter of good and evil, in charge of maintaining equilibrium, and is the more straightforward justice-themed character (his boss fight using attacks like "Dikè", his name literally being themis)
emet-selch, of course, frames the recreation of amaurot as a (literal) trial by fire, and his presence all throughout the narrative places him as the adjudicator of mankind's worth and future (partly why he's the exarch's foil). sophistry is a more developed facet of his presentation, compared to all the other ancients; he even employs the term of "moral relativism" (which he clearly presents as mere lawyer chicanery: "yes, yes, moral relativism, and all that - case on point: i do not consider you to be truly living, ergo i won't be guilty of murder if i kill you"). there is something of the dramatic lawyer about him, and his boss fight does remind me of an appeal to the jury (or witnesses maybe?) when he calls to the shades of the ancients
lahabrea too, and surprisingly enough to me at the time, is associated with justice, through pandaemonium (THE prison!), not to mention the fact the narrative of these raids takes the form of an investigation which then turns into a kind of cold case/murder investigation (grasping at straws here but the idea of the cursed bloodline, foundational crime of hubris, parental crimes, and reveal that one was the perpetrator of the crime one was investigating - if only symbolically - reminds me of various greek tragedies, including oedipus rex, which explore themes centered around justice, guilt, punishment, and mortal & divine retribution)
hermes/fandaniel (as justly noted by the one and only @fandaniel) set up the meteia as a supposedly neutral scientific project, before using their answers as material to put mankind on trial, going so far in his quest for impartiality as to let kairos erase his own memories too, before fighting on mankind's side (as a prosecutor turned defense attorney?); an action which was subtly foreshadowed since the beginning of the elpis arc, since his question has always been: "what is justice and what right have we to dictate which beings deserve to live or die?"; essentially the question lying at the core of most plato dialogues
hythlodaeus may not fit as neatly as the others here (arguably he never *did* truly fit in anywhere), but i think you could argue his role as chief overseer of the bureau of the architect puts him in a judge position nonetheless, as he is in charge of ruling over the future of each new concept submitted to the bureau for approval; most notably, alongside venat, he's the one who encourages the warrior of light to make their own choices, seek out their own answers, make up their own mind, and to live
honorable mention to the woman who would become azeyma, and of course, azem themself (more on that later IT WOULD SEEM???)