The battle between Earl Rognvald and Earl Thorfinn - Arnórr Jarlaskáld

I saw both my goldbestowers,
Each the other s henchmen hewing,
On the fitful firth of Pentland;
Thence my grief grew more and more;
Sea was blood-stained, black kept dripping
Gore between the gaping seams,
Sweat was shed on rim of shield,
All the sides with blood were dabbled.

The lord, so brave in burst of battle,
Then had surely laid beneath him
All that ancient land of Orkney,
— He had far less loss of men, —
If the sea-king son of Endil
Could have brought that host to help him,
Island-born, but Shetland s lord,
By his army was betrayed.

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Arnórr Jarlaskáld (1012 - 1070) Iceland
From Orkeyinga Saga, chapter 31 (this was written by an unnamed Iceland author in the 12th century, and he is here quoting "the Earl's poet Anor")
Translated by by George W. Dasent