This list is a work in progress, because I like to reread fics before I rec them and I'm not rereading 20 fics in one go lmao.
For Mashmorgan fic recs, I will redirect you to the MashMorgan shrine.
FATE/STAY NIGHT
a knight on the side cannot abide , Rin/Archer/Saber threesome. PEAK characterisation, the dialogue flows so well and is so in character for everyone. It's silly. It's sexy. Archer gets to be a bitch. A++
FATE/GRAND ORDER
LB6-related
I'm Happy for You, An exploration of Guda/Castoria/Oberon's relationship. I do so love three idiots functioning under "wow these two are so good for each other! Sucks that I'll never be part of what they have".
Tomorrow's hickey, A relationship study of Castoria/Oberon via porn.
You know them like you know your own heart's beat, A Guda/Castoria relationship study. I loooove Castoria being a bitter angry rat. That's enrichment to her.
Time's Scythe, Ritsuka is stuck in a time loop in LB6. A really good take on "time loops are a pressure cooker that will slowly turn you into something completely deranged." No actually knowing how this shit works will NOT enable for an easy fix-it and it's GREAT to witness.
Good Guda content
Girl Trouble, Goredolf and Ritsuka having a conversation regarding Goredolf's previous relationship with Koyanskaya. Really good exploration of Goredolf/Koyanskaya (wouldn't it be a bitch if you genuinely cared for someone who tried to kill you twice!) and also stellar unhinged Guda with Opinions on love and relationships.
ashes to ashes, Ereshkigal/Ritsuka, with a dynamic of "man I'm the goddess of hell I'm fucked up in so many ways I HAVE to pretend to be normal"/"hehe Ereshkigal wants to take me apart and fuck my bones :]" (the author takes commissions, btw.)
The Near Enemy of Upekṣā , A surreal fic about Ritsuka Fujimaru talking to their Beast self. You guys know I'm always a sucker for some good Guda stuff, and seeing two Gudas with similar yet opposing views on things... chief kiss.
Misc
Canto III...? Bradamante bimbofication written entirerely in the style of Orlando Furioso. Yes, with the rhymes and all. An absolute flex of a fic.