okay so we know xaden killed one of king tauri's sons (halden's twin/aaric's brother) alic in basgiath and specifically at threshing because he "was a bully" and "went after garrick". what's really interesting about this though is
aaric doesn't just know it was xaden, his exact words to violet are "you have no idea what he did to alic!" and xaden's are "though i wonder who it was that told aaric, since if his father knew i highly doubt i’d still be in possession of my head."
from this wording i'd infer the issue wasn't that alic was killed during threshing (which is allowed, it's free season), it was the fact that xaden of all people killed him, and it sounds like it wasn't pretty
when violet and dain recognize aaric at conscription day, violet guesses if the king had known what aaric was planning, he wouldn't have let him go precisely bcuz of what happened to alic. therefore, it must be widely known that prince alic died in the riders' quadrant during threshing (EDIT from the replies: we know this was the case because at violet's conscription xaden's speech confirmed even a king's son can die in the quadrant, but he obv didn't say alic was killed and didn't claim the kill as his). but who would know how it happened other than garrick and xaden themselves?
it's not like cadets usually go in groups during threshing so i imagine alic was following garrick to try and eliminate him, and xaden was either just looking out for him or stumbled upon the two and did what he does best - annihilate a mf to defend his own (watching a similar situation unfold at violet's threshing must've awoken memories for xaden lol, and it also makes me wonder whether that's why sgaeyl bonded him in the first place bcuz in xaden's words she "was never fond of bullies" and i believe she's said she chose xaden for his ruthlessness)
we're not aware of any other/older cadets recognizing aaric and anyone who might've seen what went down at xaden's threshing 3 years ago no longer remains at basgiath to tell aaric personally (unless they're a repeater like sawyer??), and they could likely only communicate with the outside world by sending a letter the following year - and even if that happened, though already a stretch, why tell aaric and not halden or the king? why give details?
so i wonder if it was molvic who saw it go down and told aaric bcuz at the time aaric says this to violet, it's been just days after he bonded him (to the point where it's during aaric's thresing that violet tells rhiannon jesinia has found the vault where xaden's little fight with aaric later ensues)
EDIT from my reply: blue dragons are supposed to be the more intelligent and wise breed (remember the king is referred to as King Tauri The Wise, but ofc he's not a rider, and halden and alic don't seem particularly wise, but aaric does) so it's possible molvic was looking to bond xaden, not alic, but seeing xaden kill him in cold blood, he let another, more brutal blue do it - sgaeyl, and it was only years later that he found what he was really looking for in aaric
