Fifteen Mokona on a Dead Man's Chest by Psiten is a massive ongoing CLAMP works crossover series. Currently, all stories that have been posted are complete.
Synopsis:*
Overall: Nothing is safe. Nothing is sacred. Everything is... pirates vs. ninjas. Possibly with a bit of 'saving the world' thrown in for good measure. ''Fifteen Mokona on a Dead Man's Chest'' is comprised of stand-alone short stories that can be read independently, without going back for earlier installments. As the stories go on, however, they will consistently tie together for those who prefer to start at the beginning.
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Rum and Popcorn: So, a pirate walks into a bar and sits down next to a ninja...
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Talk Like a Pirate Day: Once upon a faraway time, in a universe slightly askew to this one, circumstances beyond anyone's control led to a fierce and bitter rivalry between Pirates and Ninjas, but Kurogane doesn't care about that. His only concern is to retrieve Princess Sakura and Syaoran from the Pirate King's ship... where Fai is happily making his life complicated.
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Slings and Arrows: Doumeki is pretty sure this is a dream, no matter what Watanuki has to say about it.
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You Got It: Life at Green Market is never easy, but Kazahaya definitely didn't ask for all this crap. And that went double for thigh-high stockings.
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Dark and Stormy: A full-scale pirate rebellion in Sorata's home fleet finds the Dragon of Heaven in a sea battle, Kamui in a race with an elite ninja team for a legendary artifact, and Fai... on a date?
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Dim Smitten Star: In which Seishirou is a jerk, Subaru is an overcooked angst-muffin, and Kerberos wishes they had worked out any of their issues in the last two thousand years.
** Although most stories in the ''Fifteen Mokona on a Dead Man's Chest'' series can be read independently, this one-shot was intended as a "post-credits" bonus scene for ''Dark and Stormy'' and takes place the night after that story ends. Its tone and focus were different enough that the author decided to post it separately, but readers may decide it benefits from context.
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Let the Games Begin: Give Nokoru an excuse, and he'll give you a festival -- with the ninja elite from every corner of the globe. Which is, naturally, where Pirate King Fai D. Fluorite wants to send Kamui this week... Nothing can go wrong!
Rum and Popcorn,
Talk Like a Pirate Day,
You Got It,
Dark and Stormy, and
Let the Games Begin all contain chapters featuring explicit material. Links to less explicit versions of the chapters can be found at the top of the sidebar on Psiten's
Dreamwidth account.
Thus far, characters from Magic Knight Rayearth have appeared in the first chapter of
You Got It and throughout
Dark and Stormy and
Let the Games Begin.
A world map for the series can be found
here.
The other CLAMP works that the series has thus far included or mentioned characters from are:
* Angelic Layer
* Cardcaptor Sakura
* Chobits
* Clamp School Detectives
* Clover
* Duklyon: CLAMP School Defenders
* Gate 7
* Kobato
* Legal Drug/Drug & Drop
* The Legend of Chun Hyang
* Man of Many Faces
* Miyuki-chan in Wonderland
* RG Veda
* Shirahime-Syo: Snow Goddess Tales
* Suki Dakara Suki/Suki: A Like Story
* Tokyo Babylon
* Tsubasa Reservoir Chronicle
* Wish
* X/1999
* XxxHolic
* Code Geass