8 And both his hands fast bound behind his back,

fast > firmly

9 And both his feet in fetters to an iron rack.

rack > {Iron bar to which prisoners were secured}

204.15

With hundred yron chaines he did him bind,
2 And hundred knots that did him sore constraine:
Yet his great yron teeth he still did grind,
4 And grimly gnash, threatning reuenge in vaine:
His burning eyen, whom bloudie strakes did staine,
6 Stared full wide, and threw forth sparkes of fire,
And more for ranck despight, then for great paine,
8 Shakt his long lockes, colourd like copper-wire,
And bit his tawny beard to shew his raging ire.

1 With hundred iron chains he did him bind, 2 And hundred knots that did him sore constrain:

hundred knots > (Cf. Aen. 1.294-6, where Furor is bound with a bronze chain of 100 links)

3 Yet his great iron teeth he still did grind, 4 And grimly gnash, threatening revenge in vain:

grimly > grimly, fiercely; dreadfully