Nearly all dungeons are empty.. the portals aren't ingane. You can warp to the dungeons through the game server by using the right command. However, all dungeons are nearly full empty, so it's useless to go there.
If you want to kill monsters you can either go to: Marduka (lvl 95 - 148) or CV (level 60 - 170) - and use those commands to change the drop rate and farm your equipment, it's kinda fun.