2 To that Elfin knight he bade him fly,

Elfin > {Of a race native to Faery Land (see 210.71 ff.)}

3 Where he slept soundly, void of evil thought, 4 And with false shows abuse his fantasy,

shows > appearances abuse his fantasy > deceive his imagination

5 In sort as he him schooled privily:

In sort as > [As, in the manner in which] privily > secretly

6 And that new creature, born without her due, 7 Full of the maker's guile, with usage sly

usage > practice, craft [of Archimago]; behaviour, demeanour [of the sprite]

8 He taught to imitate that lady true, 9 Whose semblance she did carry under feigned hue.

hue > appearance; colours