"People for whom gold holds no allure" isn't actually a full sentence, but a noun phrase. Like a noun, a noun phrase can serve as part of a sentence, such as a subject or a direct object.
For example, suppose I know or have heard of some people, and one of the things I know about these people is that gold holds no allure for them. (That is, they don't find gold very interesting or enticing.) Now suppose I find that very surprising and hard to understand, perhaps because gold holds a great deal of allure for me. I can express this by using the noun phrase people for whom gold holds no allure as a direct object:
I simply can't understand people for whom gold holds no allure.
Or I can express more or less the same idea by using the noun phrase as the subject of a sentence:
People for whom gold holds no allure completely mystify me.