So > (Follows from line 1: "Not so many furies did haunt that great champion as did this knight twelve thousand dolours daunt") haunt > visit; molest

5 When him the poisoned garment did enchant

garment > (A white garment soaked in the blood of the centaur Nessus, by which Hercules was killed (see Met. 9.134 ff.)) enchant > {Exert an evil magical influence upon}

6 (With centaur's blood and bloody verses charmed), 7 As did this knight twelve thousand dolours daunt,

dolours > pains

8 Whom fiery steel now burnt, that erst him armed,

erst > [at] first

9 That erst him goodly armed, now most of all him harmed.

111.28

Faint, wearie, sore, emboyled, grieued, brent
2 With heat, toyle, wounds, armes, smart, and inward fire
That neuer man such mischiefes did torment;
4 Death better were, death did he oft desire,
But death will neuer come, when needes require.
6 Whom so dismayd when that his foe beheld,
He cast to suffer him no more respire,
8 But gan his sturdie sterne about to weld,
And him so strongly stroke, that to the ground him feld.