This is the full translation of both versions; Graves' version is his own personal reconstruction, which I take issue with (I won't get into the argument here). The poem begins with a note from the Guest translation of the Mabinogion
Peniarth MS 98B:
These are the englyns that were sung at the Cad Goddeu (the Battle of the Trees), or, as others call it, the Battle of Achren which was on account of a white roebuck and a welp; and they came from Hell, and Amathaon ab Don brought them. And therefore Amathaon ab Don, and Arawn, King of Annwn (Hell), fought. And there was a man in that battle, unless his name were known he could not be overcome; and there was on the other side a woman called Achren, and unless her name were known her party could not be overcome. And Gwydion ab Don guessed the name of the man, and sang the two Englyns following:
"Sure-hoofed is my steed impelled by the spur;
The high sprigs of alder are on thy shield;
Bran art thou called, of the glittering branches."
"Sure-hoofed is my steed in the day of battle:
The high sprigs of alder are on thy hand:
Bran by the branch thou bearest
Has Amathaon the good prevailed."
Peniarth MS 2, The Book of Taliesin
I was in many forms
before I became free...
I was a narrow, blood-stained sword;
I believe that when I was made
I was drops in the air
looking up at the stars,
a word in a letter.
I was a primeval book;
for a year and a half
I was lanterns of light.
I was a bridge spanning
sixty river mouths.
I was a hunter's course,
I was a coracle
in the waters.
I was fizz in a brew
laying men low;
a drop in a shower of rain.
A sword in hand I was,
shield in battle.
For many years
I was a string in a phantom harp.
Foam on water,
spark in a fire.
A log in a blaze.
I am not but that I sing,
I sang since I was a small lad.
At the Battle of the Trees
I sang in the van
before the King of Britain.
I goaded on horses,
fleet of foot.
I fermented fleets
laden with merchandise.
I pierced a scaly monster.
A hundred heads it had,
one mighty host
under the base of its tongue,
in the ridges of its neck;
a black-groined toad
with a hundred claws.
Then a variegated, ridged serpent
a hundred souls are tortured
in the folds of its flesh.
I was at the Castle of Nefenhir
when trees and grass
were locked in combat.
Minstrels sang, armies collided.
Trees rose up
before the waver of a magic wand.
We called upon Neifion,
upon Christ from the first causes
so that the Lord would redeem
what he had made.
The Lord answered through the people
and the earth:
"Conjure up majesic trees",
"in great numbers
and resist the mob".
When trees were conjured up,
there came a mighty, bounteous host:
hope itself approached.
Plucked out of four kinds of strings
in battle they fell
three battle weary whelps.
The battle-cry racked a woman's heart,
tortured by grief.
Like flaxen tips
the maiden's hair,
the spoils of the heifer of unrest.
They did not succeed
in dispersing us
what with the blood of men
up to our thighs.
The biggest of the Three Bloodbaths,
this, in the history of the world:
one was the outcome of the Flood,
the second was when Christ was crucified
With the Day of Judgement near at hand.
The alder at the front line foraged first.
Then, late for the fray,
came the willow and the rowan-tree.
The prickly blackthorn with bubbling zest,
the blackberry, its royal equal,
taking the position of the heir-apparent
in the thick of the fray.
Rose bushes now ventured forth
with venom against a host.
The rasberry came forming a circle
for the defense of life.
Now privet and honeysuckle,
ivy in its prime,
then the surge of the giant gorse.
Cherry trees had sounded the alarm;
With great pomp was the birch-tree there
donning its armour, not out of cowardice
lingering there, but decking herself for the occasion.
Almond trees arose, exotic trees with foreign nature.
Pine trees took over the centre of the hall:
in the chair of honour did the oak-tree
cut a dash before kings.
Then the lime-tree in all its splendour,
not flinching one foot,
cutting them down left, right and centre.
Hazel trees were now deemed worthy for the fray.
Blessed be the privet, battle-bullock,
king of the world.
Beeches excelled on sea and estuary.
The holly has put forth leaves anew,
now at its best revelling in its battle-cry,
terror dealt from its hand.
A burst of bryony...
it has broken its ranks;
bracken's swell, broom heading for battle
in the furrows of wounding.
Gorse the farmer's bane,
yet were they gathered together.
Heather was deft & victorious,
your warriors all bewitched.
The black-cherry in hot pursuit;
the oak rushing headlong...
before it heaven & earth did shake.
Borage, inveterate fighter,
its name is on the tablets.
The convocation of elms caused terror,
they rebuffed all onslaughts
whenever their defences were breached.
The pear-tree wreaked havock
on the field of battle.
The thorn-apple was awesome,
its advance was constant.
The thrust of the chesnut
put pine-trees to shame.
Jet is wont to be black;
The mountain curved.
Trees are usually slim.
More powerful are high seas.
Since I sensed the time of year
the tips of birches have covered us over,
have undone winter's dying.
The tops of oaks have ensared us
through the Gwarchan of Maeldderw.
the lord is in full battle array.
I was not born of father or mother.
My blood, my creation
stems from the nine forms of essence
from the fruits of the earth,
from the first fructification of God.
flowers of the heights,
flowers of trees & shrubs,
from soil, from earth, was I made;
from the water of the ninth wave.
Math conjured me up
before I became the gifted one,
Gwydion witched me,
the great Brython king,
& so did Eurwys & Euron,
yes, Euron & Modron
& a hundred & fifty wizards.
Learned men like Math fashioned me.
A chieftain created me
when he was half burnt.
Wizard's ways conjured me up
before the beginning of the world:
before its inhabitation was mine,
before its extent was made.
The gift of a fine poet made us all.
In song do I abide
by what the tongue utters.
I played in the hearthlight,
I slept in purple.
I was in battle array
with Dylan the scion of the wave;
in the encirclement
right in the centre of things:
upon the knees of kings.
Like two inordinate spears
did they come from heaven
to the torrents of Annwfn:
to battle do they come
eighty thousand strong.
And I pierced them through
for all their aggression.
They are no older or younger than me
in their attrition.
The vigour of a thousand men was mine,
the cleaving of all around.
On my silvery sword,
the blood of nobles flows towards me.
Through the instigation of a lord,
through a craven's will
in his haunt a boar was killed.
He made things, he unmade them.
He made languages.
Radiant is his name.
Llwch, he leads a host.
"When I come sparks fly high".
I was a multicoloured serpent on a hill,
a viper in a lake.
I was a sword in the hands of princes.
I was a spit.
These are my cloak and cauldron:
I am well-prepared.
It brings eighty whiffs of smoke to all.
A hundred slave girls
are the value of my knife.
Six golden horses
are a thousand times better.
My light chestnut horse
is as fleet as a seagull.
I was not taken aback
on sea and shore.
I have caused carnage,
the blood of a hundred men
is on my hands.
My shield is studded with gems,
my shield-strap is gold.
In the gap was not born
a name so dear to me
but Gronw from
the meadows of Edrywy.
My fingers are long and white,
far from a shepherd was I reared;
I rolled on the ground
before I became a proficient.
I traversed, I went round them,
I slept on a thousands islands
I took a hundred forts.
Wize druids, prophesy to Arthur
what will be, what is,
what was once to be perceived:
the story of the flood,
With Judgement Day at hand.
We would extol in golden tones.
I would conjure up shrubs.
For I am wanton
with the prophesy of Virgil.
The first poem is taken from The Book of Taliesin which dates from around 1275. It is one of the transformation poems. The text is as translated by Meirion Pennar. (The prologue I obtained from an old, unabridged version of Lady Charlotte Guest's notes on her translation of The Mabinogion. It is said to be from the Myrvian Archaeology, and I have since found--through Rachel Bromwich's work--that it is from Peniarth 98B.
The poems seem to be about when Amaethon and Gwydion stole magic animals from Annwfn, and battled Bran, the Fisher King of the Grail Romances. It is similar to the Mabinogion tales of Bran and Gwydion: in the first, Bran is killed when fighting for the cauldron of rebirth, but is alive in the form of his "wonderous head," in whose company is Taliesin, Manawyddan fab Llyr, and Pryderi, the hypothetical hero of the Mabinogi, who is a sort of innocent, blundering through his adventures, and left in charge of the swine of Annwfn by his late father, Pwyll, given by Arawn, lord of Annwfn, the Otherworld. It is possible that "Arawn" is a role, not a person, and that Bran is King of Annwfn. Hence, the poem is a retelling of pieces of the Mabinogion, and the Mabinogion is an early version of the Grail quest.
Much of the poem is obscure, of course. There are allusions to Modron, Bloddeuwedd, Dylan, and other figures from Welsh mythology. What it means, though, is still a puzzle.