To get into the upper levels of the Steel Citedal, you have to do a 10 floor tower quest taking anywhere from 6 hours all the way up to 11 hours.
Once there, you have access to a few different raid bosses. To progress you need to do a number of certain quests. To get into the 2nd tower, Naia, you need to defeat Darion as seen below.
Once there, the Tower of Naia has 20 different rooms.
The way to enter the Tower of Naia:
You should attack the Lock on the roof of the Tower of Naia. When its HP has decreased to a certain degree, the Controller will be switched on . The Controller can teleport you to the waiting area on the third floor of the Tower of Naia.
When attacking, the Controller will point out that the durability of Tower of Naia’s outer wall is decreasing rapidly!
More and more Flava-like Wards will appear as the Lock’s HP decreases. And when attacking the Lock, keep in mind that it is weak to Fire, Water, Wind and Earth, but not to Dark or Holy. When attacking the Wards, use Sleep or Paralyze; those constructs have 16,053,769 HP and won’t die.
If you try talking to the Controller before the necessary conditions are fulfilled, i.e. before the Lock's HP has been sufficiently lowered, the Controller will disappear, and you will have to wait for a while for it to reappear.
Then push the button (the upper link) on the Controller's dialogue screen and you will be teleported to the waiting area from where you start into the first room. The Controller will vanish and reappear after 20 minutes. Then the next party can start on their way through the 12 rooms of the Tower of Naia.
Structure of the Tower:
The Tower of Naia has three floors (from where you battled Darion to the killing ground at the core of the tower). Every floor has several rooms, twelve in total, that are basically break-through dungeons which can only be entered by one 9 person party at a time.
There is a five minutes time limit for each room, so you must clean out the room quickly. Otherwise you will be teleported back to the roof. It should be very easy. As there aren’t any trapdoors or anything like that, you can just fight your way through.
There is an Ingenious Contraption in each room. When you talk to the Ingenious Contraption and click on "Push the button", you are setting off a counter. From then on you have 5 minutes to clean out the room. If you don't finish within 5 minutes, the whole party will be teleported back to the roof.
When the entrance door closes, designated monsters will appear in different rooms. (The exit doors will stay closed). After clearing the room, the exit door and the entrance door to the next room will be opened, but the entrance door to the current room will stay closed.
Monsters: Beleth’s Follower , Beleth’s Devotee
Monsters: Beleth’s Assassin (aggro, 175,620 HP, has resistance against Dark attacks, can stun):
Monsters: Beleth’s Minion
Monsters: Beleth’s Assassin
When the Assassin’s HP has sunk below 50%, it’ll run to the end of the room and bring back the monsters of the entire room, so you must kill the Assassin before it reaches the end of the room
Now there should spawn Beleth's Retainers who have mastered a Spellhowler's Death Link which afflicts you with their own pain - the lower the Retainer's HP the more powerful the effect. Apart from that the Retainers like to use Dark-backed close-distance physical AoE attacks with a high crit rate.
There are two kinds of Beleth's Devotees which both use Dark-backed long-distance single target and AoE magical attacks as well as close-range Dark-backed magical AoE attacks.
One of the two Devotee varieties has the ability to summon you into that close range.
And there are also Beleth's Followers who are good at close-range single-target physical attacks.
After you have killed those, one or several of Beleth's Fighters should spawn, a heavily armored demon that can paralyse you but strongly resists itself Sleep, Hold or Paralysis spells. In addition to that it is good at Dark-Backed close-distance physical AoE attacks.
Once you have killed the last Fighter, the exit door opens and you can descend to the second floor.
In the 6th room you only have to deal with one kind of monster - Beleth's Projection. As mentioned above, they are heavily armored healers.
They can buff themselves with the Ogre Spirit Totem, which means increased P.Def. and M.Def. They have a Dark-backed physical long-distance AoE attack and a nasty Stun, while they themselves strongly resist Hold and Paralyse spells.
Interestingly enough they are not especially resistant against Sleep, so this might be a way to get the better of them.
In the 7th room you will encounter Beleth's Followers and Beleth's Devotees again. Once you have killed them all, one or several of Beleth's Fighters will spawn. Kill them and you can descend to the next floor down.
The 8th room is a Danger Area with poison debuff. In there you have Beleth's Projections again.
The 9th room is a "healthy" environment. All you have to deal with are Beleth's Minions. There are again two varieties. Both are good at physical close-distance AoE attacks. The one variety has in addition to that a single-target physical close-distance attack, while the other one stuns. Again both have a strong resistance against Hold and Paralysis, but not against Sleep.
The 10th room is again a Danger Area, this time with fire debuff. The mobs in there are Beleth's Projections.
In the 11th room you will be confronted with a new monster - Beleth's Low Servant. Those guys have spells for lowering your movement speed and to paralyse you. Especially their latter skill is quite impressive, therefore don`t to forget to put on stun resistance buffs before entering the room.
Attack the Low Servants specifically with Mages and above all use Sleep on them whenever possible.
In the 12th room you will encounter Beleth's Slaves who are using nasty magical shockwave attacks, both long-distance single-target (Dark-backed) and close-range AoE (without Elemental Attribute). The little dolls have only 29,293 HP, but they always come in groups and they have a tendency to blow themselves up in spectacular explosions.
After you have fought your way through all 12 rooms you can descend to the bottommost floor with the Mutated Elpy.
You have entered the Core of Naia - the Raid Boss killing ground.
And this is the place where you have to wait for your comrades. Only one party every 20 minutes can fight their way through the 12 rooms.
That means the first parties have to wait for a very long time until the 200 people required for a successful Beleth raid have one after another arrived.
If only one member of a party logs out or gets disconnected from the internet, the whole party will be teleported back to the Oasis near the Enceinte. So make sure to bring some more than 200 people along. The minimum number to get the Raid Boss Epidos to spawn is 27 people.
When everybody has arrived, hit the brown bunny. It dies immediately (like the mini devils in the Wishing Potion quest) and spawns a bunch of Naia Spores. In this moment the door closes behind you, no further members of the group can come in, and the 4th floor (counting downwards) turns into a Danger Area.
There are four kinds of Naia Spores, corresponding to the four Elements:
Fire, which looks like a Salamander from the Forgotten Temple
Earth, which looks like a Golem
Water, which looks like an Undine from the Elven Ruins
Wind, which looks like a Babbling Wind from
All of them strongly resist Sleep, Hold and Paralysis, have a strong attack power that they use for single-target close-range physical attacks backed by their respective Element, and turn up at a mind-boggling spawn rate.
In addition to that the Golem Spores are heavily armored.
If you kill Spores of one Elemental Attribute, the Epidos Index for that Element goes up. If you kill a spore of the opposed Element, the Epidos Index goes down a considerable way (like killing an Undine Spore while aiming for a high Fire Index). If you kill a Spore of one of the other two Elements (in this case a Golem or a Wind), the Index goes down a bit.
When the Epidos Index has reached a certain level (after about 30 minutes) the Spores will run together at the energy column/ball in the center of the room and so to speak "coagulate" into an Epidos of the opposed Element.
Since the formula by which the Epidos Index is calculated is very complicated and only killing one kind of Spore is easier said than done, you may be unlucky and in spite of all your efforts never get an Epidos to spawn. One method to increase your chances is to first kill two kinds of Spores. When for example the Earth and Wind Spores are gone, it will take a few minutes until new ones are born. You can use those precious few minutes to kill one of the remaining kinds of Spores and drive the Epidos Index up to a level where the creature spawns.
Keep in mind that time does play a role. If it takes you too long to drive the Epidos Index to the level where the creature gets born, you will have to kill a new Elpy again. This is no reason for despair. In fact, if you have in your first round for example killed a lot of Earth and Wind Spores, chances are that in the second round there will be less of these two kinds and you can better concentrate on one of the remaining, for example Water.
All four Epidos resist Bow attacks, look basically the same, just a slightly different color, and they have attack skills of their own Element. Like the Fire Epidos throws grenades with his right hand, it reduces with a curse your resistance against Fire and gives you a burn damage over time like the Salamanders in the Orc Cave of Trials.
Be aware that you have no breathing space. The Epidos will spawn immediately after you have killed the necessary number of Spores. There is no time to rest and recover HP/MP, especially since you are in a Danger Area with a debuff that constantly drains your blood.
There is also no safe place in the rather small room where you would be out of the Epidos' reach. Recommended isto bring an Eva's Saint along who has learned the lvl 81 skill "Blessing of Eva" which recovers HP/MP and cancels bad abnormal conditions. A Cardinal with the lvl 78 skill Cleanse would certainly be helpful too.
After you have killed the Epidos a Teleportation Cubic will appear that is supposed to teleport your whole group into Beleth's throne room.