There are two 10+ Floor Dungeons in Quarantine. They are as follows:

Delta: Reincaranted, Purgatorial, Alter (You fight Cubia here for the last time. He is pretty tough, so level up. You will also fight Corbenik. Both of them are tough, and you fight one after another. These are the final bosses. This is 10 floors.)

Omega: Hidden, Darkside, Holy Ground (This is an extra area. It has exactly 15 floors. You face two guys at the end, and their tough.)