A riddle from the past

Amergin Glúingel was a prince, druid, and bard who along with his two brothers, led the Milesian Invasion of Ireland which historians speculate occurred several centuries before Christ. But no one knows for sure. 

According to Irish mythology, the druids defending Ireland raised a storm a to keep the Milesians from landing at the harbor.  But Amergin sang an invocation calling upon the spirit of Ireland, which came to his aid, and calmed the waters.  The Milesians landed, brought the defenders to battle, and triumphed after heavy losses.

According to a flier I encountered on SE Main Street, the verse below is ascribed to Amergin.

I find it haunting, solemn, and weighted with a perplexing certainty.  How about you?  (Especially my Irish friend.)

The Mystery

I am the wind which breathes upon the sea,

I am the wave of the ocean,

I am the murmur of the billows,

I am the ox of the seven combats,

I am the vulture upon the rocks,

I am the beam of the sun,

I am the fairest of plants,

I am the wild boar in valor,

I am a salmon in the water,

I am a lake in the plain,

I am a word of science,

I am the point of the lance of battle,

I am the God who created in the head the fire.

Who is it who throws light into the meeting on the mountain?

Who announces the ages of the moon?

Who teaches the place where couches the sun?

(If not I)