OKAY
SO
skulk au was based off a plotline from the i forgor rp that ended up not continuing to the current time. you can read back and discover skulk arc for yourself if you want, but the basics are:
gang finds fundy, bro is really really traumatized
main source of comfort is this skulk guy named san, who seems to be passive (spoiler alert: he's not)
scientists are alerted, gang runs, finds their way underground
tunnel exploration yay
fundy and san explore tunnels, find skulk, find giant cavern with ancient city
san yeets itself off a cliff, fundy thinks he's dead and mourns n stuff
san is fine, but fundy's bitch crying summons warden
boss battle music starts playing
they kill the warden (san fought valiantly. fundy.. i mean he threw rocks and it worked)
san munches on warden's soul cache (basically an organ), offers some to fundy
fundy, being lil stupid dum dum, joins in the munching
san and fundy go and explore ancient ruins
mauve just.. chills in the cavern and lets them do their thing, rest of the gang is off in other various sections of the cave system
fox and skulk dude bonding session heartfelt moments no cap
BUT tubbo decides to be a little BITCH and gets san all pissed
san fucking kidnaps tubbo and asks fundy to kill him
fundy's all like "no i have morals" and san's like "who tf does this bitch think he is whatever i'll just use mind control until he comes around"
yeah that's the main stuff, way more things happen (GO READ RP!!) but i'm not writing all that shit down. basically they defeat san with the power of love and friendship (ranboo goes fucking feral on his ass) and san goes through portal to do skulk expansion things after heartfelt speech to fox boy. fundy eventually gets kidnapped and the skulk is surgically removed from his system.
skulk au is a little what-if thing i had that eventually turned into a giant thing, and it's all based on one question: what if it had worked? what if the skulk spread just a little bit faster? what if events played out just a little bit differently? (actually, that's three questions, but you get it.) there's a separate version of this au i developed recently where the surgery was done improperly and just a bit was left, leading to fundy going back to the smp and eventually being overtaken. i like both versions, but heavily prefer the former. it's the original one, so i have the most developed lore for it. plus, san's only in the og au, which makes it WAY more fun (shoutout to "evil guy adopts brother" tropes)
in the main skulk au, fundy ends up doing what san asks. he kills tubbo, and most of the rest of the gang is kidnapped. insert details here. san and fundy eventually (as in a few weeks later) make their way up to the main facility. a giant scientist massacre ensues, along with some c!salmonduo stuff. so far, the au is pretty open-ended. can't decide if i want to give these guys a happy ending or no.
but.. yeah, that's skulk au in a nutshell :D