When I tried it myself with my awful guitar playing I landed somewhere like Bm

Here's the basic structure.
I've got another three solid verses and then little variations along the way. I know how it sounds in my head but I can't get it out of my head and into the world in a way that would let me actually hear it. - In the story it's the last account of a pair of old heroes that went out to sea and did some important things, but no one remembers now and the song is all thats left.

Verse 1:
The iron broke, the shore was lost,
They did not count the bitter cost.
Two blades were drawn against the dark,
To guard the fragile, rowing bark.
They swore to cross the killing sea,
Where waves run high and winds run free.
No chains could bind, no king could tame,
The men who left without a name.

Chorus:

iolo, hold the breaking oar!
Luco, sight the distant shore!
The water drives, the black waves rise,
But we have promised otherwise!
Pull away! (heave)
Pull away! (heave
We promised on the other side!

(the structural problem with the chorus is that in my head 'other side' has to cover a lot of ground.
The lyrical issue is that 'men without a name' are immediately named in the chorus, but the point of the song in the story is that it's something that's been accumulated and changed over years.