(Arthur is sometimes replaced with Melwas which makes no sense. for
In 'Culhwch_and_Olwen' Arthur made fun of Kai and 'thereupon Kai was wroth, so that the warriors of the Island could scarcely make peace between Kai and Arthur'. So Arthur and Kai were in competetion.
From The Bardic Museum byEdward Jones Publication date 1802
Black is my steed and bears me well;
Nor will he the water shun;
And no man will be retreat!
Bright is my steed of nature's hue:
May the boaster always be despised;
He only is a man, who makes good his word!
Who will ride and will be firm?
Who will march in front of battle?
None but a hero can overcome Cai the tall, son of Sevin
I will ride, and will be firm;
And will march with speed along the bank of ebbing tide:
I am the man who will overcome Cai!
Hold youth! It is strange to hear thee,
Unless thou art more than thy appearance;
Thou couldst not overcome Cai with a hundred in thy train!
Gwenhwyvar of the beauteous look,
Deride me not; though small I seem,
I would myself a hundred take!
Ha! thou youth, in black and yellow grab!
From having steadfastly viewed thy form,
Methinks I have seen thee before!
Gwenhwyvar of sweet looks of mildness,
Inform me, (if thou knowest)
Where didst thou see me before?
I saw a man of moderate stature
At the long table of Kelliwic, in Devonshire,
Distributing wine to his friends around him.
Gwenhwyvar of charming discourse!
From woman's lips, we look for idle talk:
There, truly, thou hast seen me!