Despite decimating most of the monsters that appeared in the portal, their numbers seem to not have reduced at all. More like they have increased more of their numbers every time we kill one. I also noticed that my exp counter is not increasing. Even though we are killing more than usual, I am not receiving a single experience point, not even a 0.5 or 1 exp point, nothing at all. It kind of pisses me off, but I think this was designed since the portal is releasing multiple enemies every time, and having a high leveled enemies spawned, it might make a good place to farm. To avoid that from happening, they remove the experience you receive from killing them all.