Meaning of sentence in Frankenstein

Solution 1:

Examining the sentence, which says "I beheld my person", it mentions two ways in which the speaker does that:

a) reflected in water

b) shadow in the moonshine

The two phrases further on in the sentence, about which you ask, refer to those two images, respectively:

a) that frail image (reflected in water)

b) that inconstant shade (the shadow)

What "even as" does, is to say that the speaker's appearance was horrible, even when seen indirectly in those ways.

So to paraphrase the sentence:

I hoped that I did not look awful, but even mere suggestions of my appearance were enough to destroy that hope.