BlackIce

BlackIce is the slash ship between Pitch Black and Jack Frost from the Rise of the Guardians fandom.

Guardians of Childhood (book series)
In the original books Jack Frost is the transformed Nightlight, who was Pitch's rival long before the guardians were formed after Pitch escaped the prison both he and Nightlight became trapped in.

Rise of the Guardians
Jack and Pitch were aware of one another's existence, from their reputations as Jack Frost and the Bogeyman, but their paths didn't cross until the Man in the Moon decided to make the young winter spirit a guardian. Knowing that the four main Guardians need Jack's help in their battle against Pitch Black.

When Pitch first saw Jack with the Guardians he found it amusing, knowing that Jack wasn't the type the to hang out with the Guardians, with Jack having no believers of his own. Something that Pitch could relate to when the Guardians ended the dark ages and kept him from being seen by mortals. Knowing that Jack also longs to be believed in and to no longer be invisible to the children he plays with, Pitch decided to take advantage of it. Sensing that Manny has chosen Jack for a reason and would rather have the winter spirit on his side. His suspicions get proven from seeing Jack's ice powers being able to freeze Pitch's nightmare creatures and how powerful he is without the strength of children's belief. Having him see Jack has someone who knows how to have fun.

After is first attempt to get Jack and convince him to switch sides failed, Pitch tries again while ensuring that Jack wouldn't be able to help the Guardians ensure that Easter doesn't get ruined. Jack being confident that Pitch is no match to him and his staff was what made it easy for the Bogeyman to find Jack on his own and away from the other Guardians, with Jack believing that he would return to them the second after he brought Sophie Bennett home, and had faith that if he should find himself crossing paths with Pitch on the way back to them he would be able to take him on without any trouble. Once Pitch found Jack's tooth box that contains his long lost human memories, he uses the voice of Jack's she little sister to lure the winter spirit right into his lair. Where he was waiting for him and prepared to use Jack's memory box as a burgeoning chip. Jack didn't want to side with Pitch and kept his guard up as Pitch uses Jack's fears to break him. Along with the Bogeyman giving Jack his memory box to plant the seed of doubt among the Guardians, so they would turn their backs on the winter spirit.

Fanon
Despite the large age gap between them and the fact that the two are enemies, BlackIce is a well liked slash ship within the RotG fandom. Thanks to the group who enjoy "Hero x Villain" ships, who sometimes have Jack as a darker version of himself and sides with Pitch; by choice or corruption through Pitch's nightmaresand. This idea had inspired few to create an AU that has Jack as Pitch's son, since Pitch's book counterpart is a father and his daughter was transformed into Mother Nature, making the idea not so out there. To keep it from becoming a target for ship haters, some people make Jack older and more around Pitch's age, or have BlackIce as a friendship instead.

There have been a few fanfics of Jack being found by Pitch not long after his transformation into a spirit, along with featuring Pitch as a kind or abusive foster parent, uncle or guardian that takes Jack in. The idea is mostly seen in Modern AU's, that have the two as normal human people rather than spirits of legendry, mythical figures.

Pitch being Jack's arch enemy and the his connection to Jack, has him serving as the main villain of the  fandom. By having him targeting the rest of the Big Four (Hiccup of How to Train Your Dragon, Merida from Brave and Rapunzel from Tangled) to harm Jack. From time to time, Pitch has appeared in a few AU scenarios with Jack. That either keeps the two as enemies or features as friends, father/son, uncle/nephew or guardian/ward. For example, in the popular Hogwarts AU, that sometimes mirrors the Harry Potter plot, Jack is placed as a Harry-like character while Pitch serves as his Voldemort. While a Hotel Transylvania AU sometimes has Pitch and Jack as Drac and Mavis.

On AO3, BlackIce has over 1,237+ slash fanfics.

Fandom

 * FAN FICTION