The statement below is false.
The statement above is correct.
What about 2 trogs and one Demon? Trogs=1 enemy, Demon=1 enemy. So he can block the Demos OR the trogs? Am I right?
He blocks all of them. They're not checked simultaneously, but rather, whenever any enemy (be it demon or trog or hellhound) wants to leave, the Impressive talent keeps them from doing so. It's not exhausted after one use or something like that, the impressive guy doesn't stop being impressive after he impressed one (kind of) enemy.