An allusion to Spenser; compare the epigram "On the Bear Fac'd Lady" by Samuel Wesley the Elder: "He who to meet a Devil does prepare, | Like Spencer's Knight, may find an Angel there." There appears to be an error in the Spenser Allusions citation: I have not found the poem in the place cited or elsewhere among Killigrew's epigrams.
Thou wert all Painting, Garniture, and Fan;
Lame and mishapen oft; and didst disclose,
Thy Beauty not in Features lay, but Clothes,
And while to be fair Una thou didst brag,
Uncas'd, thou art Duessa, and a Hag.
[p. 73; Wells (1972) 306]