Arguably the second hardest dungeon in the game, second only to the Tomb of the Ancients, the Ocean Trench can be one of the most rewarding experiences in the game. However, it is also one of the deadliest experiences in the game; time here is not on your side.
The portal to the trench is dropped 100% of the time by the Hermit God, an event which spawns once per realm. This makes mana pots rather rare and in heavy demand. The Hermit God itself drops T2 potions, or dex, wis and vit. Although it?s SB threshold is high, it can drop multiple loot bags, with the highest seen being 4.
After entering the portal, the player is spawned in a large air patch. Like the Abyss of Demons, the entrance is quite dangerous, and fatalities are not uncommon here.
After entering, watch out for fishmen warriors or giant squids being dragged to you.
The layout of this dungeon is similar to that of UDL. Although there are multiple paths, it is not a labyrinth like the Abyss of Demons. There is a single pathway to the boss chamber. There is a minimal of one air pocket in every room. Take care to note their locations, and attempt to clear them if you are not rushing.
The boss chamber is a fairly large circular room with four pillars. There are four air pockets guarded by Deep Sea Beasts. It is advised that you do not use those unless you have extremely high defense or is in a large group. The Deep Sea Beasts re-spawn within 10 seconds after being killed, and have 15k HP, so it?s not worth killing them.
The boss chamber, where Thessal resides
Fishmen: The minion food of ocean trench, fishmen are fairly deadly, especially while confused. They are hardy and tough, having 2.5k HP and 40 def. They have a three shot trident attack similar to that of the Demon Warriors of the Abyss, as well as a confuse boomerang that does 65 damage. Circle or strife them if possible. If other enemies are near, leave them until last.
Fishmen Warrior (aka DAMN/Fishmen daddy): These are the deadliest enemies in Ocean Trench. They are very tough, having 10k HP and 52 def, and are also very deadly. They have a larger confuse boomerang which deals around 70 damage, a 4 shot body shotgun, and a long range 3 shot trident attack. All of these deal high damage, and must be avoided. Attack these first, making sure to avoid the confuse through circling or strafing?
Giant Squid (aka Pooper): Although annoying, these are not very deadly. They have 6k HP, and 40 def. They lay a white trail of bubbles that last for 2-3 seconds and deal 40 damage. The bubbles also probably slow. These squids also release ink bubbles (2k HP) which blind. Their attack is negligible.
Sea Mare (aka ARRRGGGHH MY MAXED ROGUE): An extremely deadly monster, make sure to kill these. They have 6k HP and an astonishing 60 def. They shoot paralyze stars 4 ways. If you?re hit by one, nexus or teleport. Kill these quickly, even before fishmen warriors. They spawn sea horses, little snotty things that are merely annoying.
The Crap Minions
Other minions in Trench are negligible. Sea slurps spawn from coral beds, while sea horses spawn from Sea Mares. both deal little damage, and no status effects.
Thessal the Mermaid Goddess
With 69k HP and 60 def, Thessal is as tough as Oryx 2. Thankfully, she?s immobile and predictable. If you?re soloing, prepare for a long and grueling battle.
DO NOT use the air pockets in this room unless you are in a large group. Clear the previous room, and use the air pocket there. Also use this room to regen and hide.
Attacks to watch for:
Coral Bombs: these horrible things deal 40 damage and split into 6 more bombs. They are very deadly to the unmaxed player. If you have max def, ignore these in favor of larger attacks.
Yellow Wall: This huge area attack is extremely deadly to the melee player. It deals 120 damage per shot, and is fairly fast. To avoid it, back up and slip between the openings, or hide behind a pillar.
Yellow Swirl: This attack deals 100 damage and inflicts armor broken, a very deadly status effect when coupled with coral bombs. Avoid these first.
Quote from Linkshot ~
There?s a trigger
It just hasn?t been mastered yet. I?m pretty sure if you kill her either right before or during the ragemode yellow waves, she?ll crumple over and go into quiz time.
Through further research, it was concluded that this is further affected by chance. Although the phase is almost certainly triggered by killing her when she?s flashing and is about to unleash her Yellow Wall attack, it does not always happen. Chance is a factor in this.
If Dying Thessal does occur, she drops 3-4 coral gifts, which each contain, at the very least, a coral juice.