If you are upgrade at high level in Atlantica, such as level 90-95. There are kinds of bosses here, we will introduce to you below, please have a look.

Dungeon Mini Boss: Broken Beast Engine
It looks like a powered up version of the Beast Machines from the Sunken Machine Shrine but it only has the gunner attack. It doesn't have the strong area skill(Atlantica Gold) like the Psychic ones. Its fairly weak compared to previous ones as well.

Dungeon Mini Boss: Kakemaru
This one is a powered up version of the Shadow Ninja from Shogun Castle of Death. It has a decent attack, but its focused so damage isn't as bad. Overall it has low HP which makes it fairly easy to kill.

Dungeon Mini Boss: Yoruichi
Yoruichi is a powered up version of the Cheering Dancer except it only attacks. It only has a single target attack as well. Although it has a decent defense and HP, its attack isn't all that powerful so you just need to out last it.

Also, there are some others, such as Raheth, Salamander.

At level(Atlantica Gold) 90 you can also start doing the daily Goonzu quest. All you need to do is go to Moscow and kill 50 Blazing Lizards nearby then turn in a Brush. Doing this 3 times will grant you access to the Goonzu dungeon for 2 hours. The Goonzu quests are difficult but the drops in the dungeon is great. The dungeon itself is only open on weekends but you can collect the passes any time. All of the rare craft.