''[[http://www.fanfiction.net/s/7649357/1/ Deep as the Sea]]'' is a ''Literature/TheDresdenFiles'' and ''Literature/PercyJacksonAndTheOlympians'' crossover by Ryuugi.
All the Demigods of Camp Half-Blood know about the [[WeirdnessCensor Mist]], a mysterious force that prevents Mortals from seeing what truly happens around them. Their deeds, powers, and battles. It keeps them safely hidden from mortal eyes. But what they don't know, is that mortals aren't the only thing the Mist hides them from. There is far more to the supernatural then the beings of Greek Myth; there are [[OurVampiresAreDifferent Vampires]], [[TheFairFolk Faeries]], [[FunctionalMagic Wizards]], and countless other creatures.
Something has happened to weaken the Mist, and while the Half-Bloods are still shielded from mortal eyes, they now find themselves part of an entirely new world. The world of ''Literature/TheDresdenFiles.''
[[https://forums.spacebattles.com/threads/percy-jackson-and-the-olympians-the-dresden-files-deep-as-the-sea.209742/ Thread 1]], [[https://forums.spacebattles.com/threads/percy-jackson-and-the-olympians-the-dresden-files-deep-as-the-sea-part-2.211072/ Thread 2]].
!!This fanfic contains examples of the following:
* CanonWelding: The worlds of ''Literature/PercyJacksonAndTheOlympians'' and ''Literature/TheDresdenFiles'' mesh together surprisingly well.
** The natural knowledge displayed by certain half-bloods (such as Percy's intuitive understanding of maritime navigation in ''The Sea Of Monsters'') is Intellectus, which is how the Dresden Files describe that exact ability.
** The half-bloods as a whole are capable of crossing into the Nevernever at will, provided they're in a place that is in some way connected to their godly parent.
*** An exception for that last part is made by the children of Hermes. Because their dad is the god of travelers and boundaries, they can cross over anywhere.
*** On that note, Luke's escape from Camp Half-Blood in ''The Lightning Thief'' is explained as crossing over.
* CrazyPrepared: It's clear that the gods knew about the rest of the supernatural world, and took steps to protect their children from it. Apart from using the mist to hide them, they made sure that Camp Half-Blood is linked to some seriously hardcore parts of the Nevernever, ensuring that they wouldn't be attacked from there.
** The cabins in particular are connected to what are basically fortresses designed around the strengths of whatever god the cabin is dedicated to. Poseidon Cabin for example leads to an endless ocean full of the most vicious sea monsters imaginable.
** These defenses have presumably been applied to [[Literature/TheHeroesOfOlympus Camp Jupiter]] as well.
* FirstNameBasis: Simon tells Percy he earned the right to call him by his given name when the demigod saved his life from a horde of ravenous vampire lords.
* ForWantOfANail: The Half-Bloods prevent the Red Court's attack at Archangel from succeeding, thus saving Simon (a member of the Senior Council and Justin Du Morne's former teacher) from dying. This in turn means that there won't be a seat open for Ebenezer [=McCoy=].
** Also, the weakening of the Mist seems to have stopped Hera/Juno from switching Percy and Jason, which means that the Greek and Roman camps are still unaware of each other, and that Percy didn't lose the Curse of Achilles.
* HumanoidAbomination: According to WordOfGod, this is how demigods appear in the [[TrueSight Sight]], with Nico and Percy being especially [[GoMadFromTheRevelation sanity]] [[BrownNote breaking]].
* NighInvulnerable: Percy still has the Curse of Achilles from ''The Last Olympian'', having never lost in it the ''Son Of Neptune''. It comes in especially handy when Red Court vamps try and fail to bite him.
* OneManArmy[=/=]PersonOfMassDestruction: Percy, as per Canon.
* SpannerInTheWorks: Camp Half-Blood's sudden presence starts messing up the Status Quo pretty quickly. First they help a group of Wyldfae establish a settlement in Faerie, then they screw up the Red Court's attack at Archangel (described in ''Summer Knight''), saving the lives of all the Wizards who were there.