Science is all about proving theories and understanding the universe. Science folds everything into neat logical well-explained packages. The fey are magical capricious illogical and unexplainable. Science cannot prove the existence of faeries so naturally we do not exist. That type of nonbelief is fatal to faries.
Im's offspring stare at stars and make clocks that calculate useless happenings like the angle of a hawk's claws as it strikes its prey. They demonstrate their contraptions and everyone marvels. My children get drunk, confuse a herd of cows with an enemy regiment, and slaughter the lot, screaming like lunatics until the entire army panics.
I also stole a small yellow doughnut from the box of Duncan's doughnuts in the rec room and fed it to the attack poodle in my office. He made a great production of it. First, he growled at the doughnut, just to show it who was boss. Then he nudged it with his nose. Then he licked it, until finally he snagged it into his mouth and chomped it with great pleasure, dropping crumbs all over the carpet.
When you want to take over a city, you have to destroy the illusion of safety it provides. You have to hit the large well-protected establishments, find the powerful people who run them and are viewed as invincible, and kill them. You want to destroy the morale first. Once the people's resolve is gone and everyone is scared for their own skin, the city is yours.