Let $\mathcal{E}$ be a topos and $\Omega$ its subobject classifier.
Is it possible to have a nonidentity local operator (a.k.a Lawvere-Tierney topology) $j\colon\Omega\to\Omega$, a $j$-sheaf $X\in\mathcal{E}_j\subseteq\mathcal{E}$, and an epimorphism $f\colon X\twoheadrightarrow\Omega$?
I'd be interested to see an example.
Thanks!