There's nothing magical about a bunch of street urchins. What I could see is a skill that causes a random super-low-level mob to jump out and attack you every time you move inside the city. So, the mob dies in a tick, but it makes it hard for people suffering from this "skill" to walk around very quickly inside the city. Or maybe instead of attacking (and dying) they just use the "push" skill to momentarily lag you and move you into the sitting position.