Cerulean Onslought leaker is a fellow redditor, I have hidden their username to abide by rules.
Over a day ago the redditor(cerulean onslaught leaker) responded to someone in the "vessel leak" post(a leak which has seemingly taken the redditor by surprise) with "Moonlight Trident". (Picture 1)
Today, well after that response, the redditor(cerulean onslaught leaker) made a part two of the "cerulean onslaught leak" on 4chan and mentioned the moonblade sword being shaped like a trident. (Picture 2)
A bit careless.
This redditor has also coincidently been the first to make posts about the cerulean onslaught 4chan "leaks" and the first to spread them further on other subs all in 3rd person and was already clearly interested and aware of past leaks such as "fmc". (Picture 3/4/5)
Lastly, this redditor has been fiercely defending the cerulean onslaught leaks such as most recently the names of the bosses and has defended against any other leaks such as dark souls 3 remaster and vessel.
No ill will here btw, looking at their history it is clear this person is just very interested in that type of mythology art etc and has been sharing them plenty.
Just something funny I noticed by looking at the account after seeing the same name defend the cerulean onslaught leaks over and over.
TLDR: Cerulean Onslaught "leaks" are false and the redditor/leaker has been posting and spreading them in 3rd person, defending and doubling down on them against user disbelief and any other leaks(dark souls 3 remaster/Vessel).