1 Behind his back he bore a brazen shield, 2 On which was drawn fair, in colours fit, 3 A flaming fire in midst of bloody field,
bloody > blood-red field > {Surface of the shield; a technical term in heraldry}
4 And round about the wreath this word was written:
wreath > {Representation of a ring or circlet used as a bearing or device; another heraldic term} word > declaration; motto, phrase
5 Burnt I do burn. Right well beseemed it,
beseemed it > [it seemed appropriate]
6 To be the shield of some redoubted knight; 7 And in his hand two darts, exceeding fleet
fleet > swift, fast-flying
8 And deadly sharp, he held, whose heads were dight
dight > decked, prepared; hence: dipped, steeped