1 Atin drew nigh, to weet what it might be;
weet > learn, perceive it > [the matter]
2 For much he wondered at that uncouth sight;
wondered > marvelled uncouth > bizarre, unseemly
3 Whom should he, but his own dear lord, there see, 4 His own dear lord Pyrochles, in sad plight, 5 Ready to drown himself for fell despite.
fell > terrible despite > rage; defiance
6 "Harrow now out, and wellaway!" he cried.
Harrow > {A cry of distress or alarm, or for help} wellaway > alas! he > [Atin]
7 "What dismal day has lent this cursed light, 8 To see my lord so deadly damnified?
deadly > mortally damnified > brought to destruction; injured