I found portions of this poem being used as an avatar, and tracked it down to a Madeleine L’Engle’s A Swiftly Tilting Planet, part of the Time Quartet. The original is said to be St. Patrick’s Rune, from the longer Lorica, a morning prayer and a prayer for protection said to have changed Patrick and his followers into deer when they were pursued.
The Faedh Fiada; or, “The Cry of the Deer.”
At Tara in this fateful hour,
I place all Heaven with its power,
And the sun with its brightness,
And the snow with its whiteness,
And the fire with all the strength it hath,
And the lightning with its rapid wrath,
And the winds with their swiftness along their path,
And the sea with its deepness,
And the rocks with their steepness,
And the Earth with its starkness —
All these I place
By God’s almighty help and grace
Between myself and the powers of darkness.