some lines about King Arthur's time

Can someone explain me the following bold points that are unclear for me?

He said, “Sir hermit, I pray you give me all my rights that a Christian man ought to have.” “It shall not need,” said the hermit and all his fellows; “Tomorrow morn you shall be well” “My fair lords,” said Sir Launcelot, “my careful body will into the earth; I have warning more than now I will say; therefore give me my rights.”
(Does he warn them or has he got a warning from someone?)

I hear the steps of Modred in the west,
And with him many of thy people, and knights
Once thine, whom thou hast loved, but grosser grown
Than heathen, spitting at their vows and thee

Modred’s narrow foxy face,
Heart-hiding smile, and gray persistent eye:
Henceforward, too, the
Powers that tend the soul
To help it from the death that cannot die,
And save it even in extremes, began
To vex and plague

Thou also hast had the world’s buffets and scorns;
And to thy life were not denied
The wounds in thy hands and feet and side
Mild Mary’s son, acknowledge me;
‘Behold, through Him I give to thee!’

All the old chronicles give the story of her devotion to her aged parent, but none of them seem to have been aware that she is destined to remain with him till the day of doom, whilst Gwyn ap Nudd, the king of the fairies, and Gwythyr op Greidiol, fight for her every first of May, and whichever of them may be fortunate enough to be the conqueror at that time will obtain her as a bride.
(Who is meant by none of them? I’m a little bit confused here.)