I found this old dinosaur while I was browsing through the old threads and I thought I'd rez it in case anyone's found new fics they'd like to recommend.
Name: The Soul Lights Continuum
Link: http://www.catstrio.de/
Author: Mysticmew
Type: Action/Drama/Romance/Shoujo Ai
Series: Sailor Moon
Crossover: Cardcaptor Sakura, Slayers, Inuyasha, Tenchi Muyo, Escaflowne. There's also supposed to be some Magic Knights Rayearth and Ranma 1/2 in upcoming chapters.
Description: In 2001, Earth is invaded and conquered by a malevolent entity known as Pandora. The last words of Daidouji Tomoyo speak of her love for Sakura, one that has gone unnoticed for years. With nothing left to lose, Sakura takes an enormous gamble and unseals the Time card, travelling back in time to live out her life with Tomoyo instead of Syaoran and try to stop Pandora by finding the other two Forbidden Cards, Love and Silence. In the process, the girls will uncover power unlike anything they could've imagined, and change history.
But the initial battle with Pandora is only a stalling action, an attempt to delay her awakening. To destroy Pandora once and for all, Sakura and Tomoyo will need the aid of powerful allies...
Soul Lights handles the burden of being a megacross wonderfully, more so than any I've ever read. The crossovers are handled completely naturally, no alternate dimensions needed; even the integration of the Slayers characters is utterly flawless. Rather than dumping all the characters in your lap at once, Soul Lights spreads them out through a series of shorter stories that make up the continuum.
'The Forbidden Cards' starts the whole thing off with the CCS and Slayers characters, then Rei, Sasami/Tsunami, Hitomi, Kagome and Sango make their debuts in 'Miko Love'. The other Senshi make their appearances in the main event, 'Foreshadowed Dusk', which focuses on a three-way romance between Makoto, Minako, and Hotaru, but the other characters begin to make cameo appearances at this point, leading up to 'Clouded Stars', the interlude between Foreshadowed Dusk and the final battle with Pandora, which has yet to be written. It's been two years since Mew updated, but I hold out hope that he'll come back and finish this epic.
Oh, and there's a few lemon side stories thrown in for good measure.