Never heard of them, the first mentions of Kosmina and Fos in vetcord was earlier this month in vetcord and the only 2 other instances I’ve seen on the forums were these:
Vetex and Tech have never mentioned them, I don’t think the AA webcomic mentions them, can’t find any trellos or little random comments from vet or tech about them, nothing other than the AR wiki and a message about them in the AR discord.
Summary
Commander Apollo of Division 1 (old and bad tempered, extremely powerful Shatter master, but also quite adept in Aether and Earth magics.)
Commander Poseidon of Division 2 (older than Arthur himself, the original
god who lived on Mount Olympus, and created his own type of magic Poseidon, as well as using god-level water magic.)
Commander Arsen of Divison 3 (old, strategic Ash Curse user, extremely skilled curse users in defensive tactics.)
The following commanders are the only ones you get to use in game.
Commander Horos of Division 4 (blind and uses the powerful Aperture external curse)
Commander Fos of Division 5 (unknown how old he is, very mysterious and never shows his face, uses Flare Curse.)
Commander Kosmina of Division 6 (missing an arm and seemingly emotionless, user of the Crystal Curse.)
Commander Nolos of Division 7 (highly intelligent, doesn’t use any real form of magic, invented his own fighting style called Draining Fist)
Commander Fulger of Division 8 (sociopathic and cruel, uses both Storm and Lightning magics as well as a powerful spear made from Cerulean Arcanium)
Commander Thora of Division 9 (loyal and extremely disciplined and considered Cursebeard’s personal assassin, uses Corrosion Magic and a magic greatsword, one of the most feared magic weapons)
Commander Ernest of Division 10 (heavy drinker, Acid master magic and a master of the magic katana.)
Although, the wiki does seem to link to a private Trello, which is possibly the old Arcane Adventures lore Trello by vetex where he put a lot of lore ideas and character concepts. However Vetex has stated numerous times that this Trello is extremely outdated and inaccurate, and information from it shouldn’t be regarded as canon unless explicitly stated by him through the lore doc or the actual games themselves.