"Allure" is already a noun: It's a bit tricky because "allure" itself is already a noun, meaning "a quality that attracts or entices."
Alternatives:
* Allurement: This is the most direct noun form, meaning "the power of attraction or enticement."
* Charm: This is a more general term for something that attracts.
* Appeal: This refers to the quality of being attractive or interesting.
* Attraction: This is another general term for something that draws people to it.
Which to use depends on the context:
* "The allure of the unknown" works well because "allure" is the noun in this phrase.
* "The allurement of the city lights" is grammatically correct but less common.
* "The charm of her smile" or "The appeal of her proposal" might be better alternatives.
It's also worth considering:
* "Alluringness": This isn't a standard word, but it could be used in some situations.
* Phrases: You could also use phrases like "the power of allure," "the quality of allure," or "the force of allure."
Ultimately, the best noun to use will depend on the specific meaning you want to convey.