What's a specific word for someone/something that you crave but could never have? Something along the lines of the usage "holy grail" [closed]

Solution 1:

There are some one-word possibilities, none perfect.

"her skin was unsheathed to lure her unrequited's eyes"

Unrequited by itself is pretty unambiguous, given that it is almost always used in conjunction with "love", but this isn't – strictly speaking – particularly grammatical.

"her skin was unsheathed to lure her beloved's eyes"

Beloved fits grammatically, but like flame in Wordster's answer, it doesn't rule out that the feeling may be reciprocated. The same goes for "her desired's", although that word implies reciprocation a bit less strongly (desire/desired carries a sense that the object has not – at least yet – been obtained), but is somewhat awkward to say.

"her skin was unsheathed to lure her idol's eyes"

Idol is pretty good in terms of non-reciprocation, but makes the person into an object of veneration, not merely love.

"her skin was unsheathed to lure her infatuation's eyes"

Infatuation is even closer but still – somewhat like idol – may imply a certain sense of obsession that mightn't be what you're looking for (and somewhat obviously this goes double or more for "her obsession's").

"her skin was unsheathed to lure her inamorato's eyes"

Inamorato is almost perfect (only establishes a one-way loving relationship, with no reciprocation implied), but is a really uncommon loan-word (from Italian, as it happens), and will make most readers pause to understand – or even look up – the word.

"her skin was unsheathed to lure her crush's eyes"

Crush – I think – is the best option for this context, since (although it technically suffers from the same flaw as flame, beloved, desired, etc.) it is usually used in the sense that the object doesn't reciprocate the feeling (or may even be unaware of it).

The one weakness with crush is that it doesn't specifically imply an emotion as strong as mature love, but could be a more juvenile feeling, like what is usually called puppy-love.