There is Nothing Without Time (Master Post)
Title: There is Nothing Without Time
Author(s): filenotch
Artist: amyeyl
Crossover: Highlander
Word Count: ~25,000
Characters/Pairings: Methos, Duncan MacLeod, Ahriman, Bobby Singer, Castiel; Methos/Duncan
Warnings: It's Supernatural. It's Highlander. People die, and it isn't always pretty.
Spoilers: Sits within Highlander canon, SPN up through the beginning of Season 4.
Summary: It split open at the blade, opening like the iris of a cat, the edges of the figure blurring into the swirl at the outside, a vortex that Methos fell into with the force of his sword thrust, a ring of laughter in his ears. "I banish you!" Methos finds himself in a world where Immortals never existed, one where all the myths in all the books he's ever read are real. The demon Ahriman has followed him, and Castiel, the living embodiment of all those myths, wants it sent back, and Methos with it.
But how do you vanquish an enemy in a dimension where neither of you exists? The answer lies somewhere beneath the weight of knowledge Methos carries with him, somewhere in the memories of every Immortal that ever lived, but it will take Castiel to find the one that holds the key: the memories of Duncan MacLeod. Castiel will force Methos to face down that death--and in return, Methos will show Castiel that there is something very different between knowing and understanding."
Author’s Notes: This is Castiel in the beginning, and Methos plants at least one of the seeds for Team Free Will. Many, many thanks to tesserae_ for the ass-kicking beta.
Link to Art Master Post: Amyeyl's great pencils
[Part 1] | [Part 2] | [Part 3]
On AO3