The little green fruit that Duncan smeared on himself was called Night Blossom Peach. Night Blossom Peach has a unique characteristic that it contains a special fragrance to it that is undetectable to normal people.
This wasn't something known to many people. Even Duncan didn't know about it until he encountered trouble due to it. This particular spirit fruit wasn't very useful to cultivators. So, Duncan had never learned about Night Blossom Peaches in the texts he read in the scripture pavilion. He merely knew the name of the spirit fruit.
If not for him having a run-in with this particular fruit during his one-month stay in this forest region, Duncan would have never known this spirit fruit to have such a unique characteristic.
Unlike other spirit fruits that are very desirable to demonic beasts, most demonic beasts often ignore this particular spirit fruit. They don't care much about it, to be honest. All, except for one particular demonic beast.
