im just wondering if there is an in game event like that thou?
Never heard of it. There is bonus exp for dungeons if you use queue system to be randomly put into a group, but no bonus if you enter with pre-made party.
Also, there isn’t any dungeon that hasn’t been cleared so far so even if it does give extra drop/exp no one can get it now.
ohh ok hehe thanks 
i was expecting more like going unexplored dungeons with special quest that had impossible type in clearing it but had a 1% chance only in succeeding ahaha