Alliteration
Alliteration is the repetition of intial consonant sounds for a particular poetic effect. The repetition of a consonant sound might contribute to the musical quality of the poem and might also enhance the meaning of an expression.

The repeated "f" of "false," "face," "fools," and "fuels" is alliterative. The pairs "false face" and "fools/fuels" point out the irony of Narcissus's situation: his own face is "false" insofar as it is not the face of the lover he imagines. The reflection "fools" him, but it also "fuels" his desire, which has been figured with the metaphor of fire throughout the passage.