Dungeon Bosses
Dungeon bosses are the hardest monsters in the game. They have drastically increased hit points, defense, regeneration…basically if you name it, they have it. They are extremely difficult to kill. There is no level restriction for mages no dungeon bosses in terms of getting silenced; however the drop rates are reduced for being significantly higher. Through the Trader of Mammon, you can buy a scroll to reduce the chance of dropping items upon death to these bosses.
Queen Ant
The Queen Ant is located at the bottom of the Ant Cave. She is surrounded by guard ants, which are aggressive and nurse ants. In addition, there is a larvae ant in the cavern behind the ant queen. If you attack either larvae ant, all of the guards in the room will aggro and attack whoever hit it. The nurse ants will leave the Queen Ant and go heal the larvae, which you cannot kill even if you get it to zero hit points. If the nurses get the larvae to full or somebody attacks the queen ant, the nurses will go and heal the Queen. Nurses cannot be slept or silenced, but can be stunned. Both the nurses and the guards respawn very quickly. Neutralizing the nurses and keeping the guards killed is the key to killing the Ant Queen.
The Core
The Core is located on the third floor of Cruma Tower. It has many guards that hit very hard and respawn quickly. It does an AoE skill that does direct damage. When it does this it will say in shout “Purging intruders.” That’s the only thing the core does, other than that it just sits there. The guards are the hardest part of killing the core.
Orfen
Orfen is located in the Sea of Spores. She roams around SoS with some of her guards and she IS aggro. Once you get her to half health, she teleports back into her lair, where there are many more guards. Her only active skill is paralyze, other than that she just hits you hard. If you do damage to her, you’ll see her calling your name out in local chat. While she’s not that difficult herself, her guards make her extremely difficult to kill.
Zaken
Zaken is located on a pirate ship on Devil’s Isle. He is unique in that you can only enter the ship at in-game midnight. To check the in game time type /time. The door is open for 2 minutes in real time. Zaken moves extremely fast, hits hard, and does a nasty drain. Periodically, players will be teleported to adjoining rooms where you aggro more monsters and have to fight your way back to the center room where Zaken usually resides. Also, Zaken is a vampire so while some have reported you can only damage him during the day that has not yet been confirmed. Thus far, only Dawn Alliance on Bartz has worked these problems to kill Zaken on the NA servers.
Baium
Baium is located at the top of the ToI. You must complete the quest An Arrogant Search to enter his lair. Once inside, you must wake him up. If you do, the entire tower shakes. Baium himself is relatively slow but hits fairly hard and does a really nasty AoE attack. In addition there are angels that attack you. Again, nobody has killed Baium in North American servers.
Antharas
Antharas, the Earth Dragon, is located at the bottom of DVC (Antharas’s Lair on the map). In order to enter his nest, you must complete the quest Audience with the Land Dragon. Antharas's only weakness is wind attacks. He has resistances to just about everything else. His skills are stomp (AOE damage around a single target), jump (AOE damage affecting everyone in front of him plus stun), and tail sweep (AOE damage affecting everyone behind him, plus stun, plus a chance to throw his targets), fear of Antharas (makes players run away and stay on the wall until the effect runs out), curse of Antharas (-15% patk, -15% matk, -40% pdef, -40% mdef, -25% atk speed, -25% cast speed, -50% movement speed, -19 evasion, -19 accuracy, -90% crit rate), Antharas’s Beam (magic attack), and fossilization (low damage but while fossilized you cannot move, use skills, or take damage). Antharas is such a beast that he requires no guards, he's hard enough to kill alone. He waa first killed in North America on October 14th, 2005 on the Gustin server.