Taking a crack at iambic pentameter here.......

~*~Shadowfax~*~

 From forts of ravaged rainbows and wrecked stars
from the inverted tunnel of red dawn
the new day's arrows glance from your hot coat
of pearl and mithril, chasing my dry night
and cleansing my tired whiteness all anew.
Your pounding wakes the hollowed crust to hope
your muscled haste fulfils my destiny.
No master am I, and no beast are you
partners we in this our fevered lunge
our separate bloods and breathings merging as
war's horns dictate our imperative dance.
And when victory's dead tree blossoms fresh
and all freed wastelands cradle their first spring
and forgiveness is the song of life
we'll cross the heaving waves still bound as one
horse and rider, winged in healing space.