There is a great Tuatha Poem, it loses its poetical quality in the English translation, but perhaps it will define that which you request: -

I have been in many shapes, before I attained a congenial form.
I have been a narrow blade of a sword, I have been a drop in the air.
I have been a shining star. I have been a light in a lantern.
I have been a word in a book, I have been the book originally.
A year and a half, I have been a bridge for passing over three-score rivers.
I have journeyed as an eagle. I have been a boat in the sea.
I have been a sword in the hand. I have been a shield in a fight.
I have been a director in battle. I have been the string of a harp.
I have been enchanted for a year in the foam of water.
I have been a poker in the fire. I have been a tree in the forest.
There is nothing in which I have not been.
I have fought, though small, in the two battles of Moytura.
Indifferent bards pretend, they pretend a monstrous beast,
With a hundred heads, and a grevious combat at the root of the tongue.
At the back of the head a toad, and on his thighs a hundred claws;
Indifferent bards pretend the truth.
I was in the forest of Caer, hastening growth of grasses and trees.
Wayfairers perceived me, warriors were astonished.
When the trees were enchantered, there was hope for the trees,
That they should frustrate the intention of the surrounding fires.
Neither of mother or father, was my blood or body;
When I was made, of nine kinds of faculties,
Of fruit of fruits, of fruit, Goddess made me,
Of the blossom of the mountain primrose,
Of the buds of trees and shrubs, of Earth of earthly kind.
When I was made, of the water of the ninth wave,
I was spellbound by Dana. Before I became immortal.
In myriads of secrets, I am as learned as Dana.
I know the star-knowledge of stars before the Earth,whence I was born.
I have slept in the royal purple. Honour is my guide.
I have played in shadows, I have been the shadow.
Profitable learning is from the Gods, of the slaying of the boards of time,
Its appearing, its disappearing, its knowledge of passing languages;
The light whose name is splendour, and the number of ruling lights
That scatter rays of fire high above the deep.
I have been a spotted snake upon a lonely hill;
I have been a viper in a lake; I have been an evil star formerly.
My cassock is green all over, I prophecy no evil.
Four score puffs of smoke, to everyone who will carry me away:
And a million of angels, on the point of my knife.
Am I not pre-eminent in the field of blood.
Of gold is the border of my shield. My wreath is of red jewels.
It is long since I was a herdsman, I have travelled over the Earth before;
I have made a circuit,
I have slept in a hundred lands; I have dwelt in a hundred cities.
With a golden jewel set in gold, I am enriched;
And I am indulging in pleasure, out of the oppressive soil.

"Do not look not for me in shadows, the true finder will see me.
He who LOOKS the hardest, SEES the least....
....Kodome calichniye ga ni jeade'en hei."
(for the true seeker there is a welcome always)