Introduction: The Gaoling Dungeon is the best place on the server to gain gold, diamonds, exp and fame. I recommend that you only go there once you’re level 17 or above, though, because it’s pretty tough. It’s a very fun dungeon to play through, though - I think everybody should experience it at some point or another. In regards to what element you should be when you go in, I think that the dungeon is hardest for earthbenders and waterbenders and easiest for airbenders, but all elements are roughly just as viable as one another. The dungeon is by no means impossible if you’re playing earth, and it’s definitely not a cakewalk even if you’re using air.
Location: 16763 33 12591, at Gaoling, near the local overland fast travel node. Gaoling itself is just south of Ba Sing Se and north of the Southern Water Tribe To get into the dungeon, talk to the NPC Tang Zhi.
Video: https://www.youtube.com/watch?v=z62P_XhsFic (timestamps in the description)
General Tip: If you ever need to heal, jump off the side of the arena into a pool of water and eat. Then, when the game says «Have they hit with a rock yet?» get topside again, or you’ll start taking a lot of damage. Most of the bosses can’t hurt you while you’re not on the arena platform, so this allows you to win any fight with ease.
Siku, the first boss: A strong, close ranged waterbender. She’s weak at range, however, so you should aim to move around her in circles and pound her with long range moves. If you absolutely need to go close to her, dash past her first and trigger her close-range whirlpool attack without being dragged in by it. She’s lethal up close: avoid her whirlpool at all costs.
Ryu, the joke: A straightforward fight that can be difficult if you don’t have enough health or damage dealing moves. Just hit him, move in circles around him and make sure to jump into a pool of water when he fills the arena with clouds of fire. Don’t be afraid to retreat and eat if you get too low.
Kanan, the only earthbender: This is a straightforward one. Just hit him as hard as you can, move side to side to avoid his attacks, and don’t get too close or he’ll knock you into the air with a close-range move which’ll deal a lot of fall damage to you. He’ll summon pillars of sandstone throughout the fight but these basically do nothing.
Katsu, the master of B.S: This is a tough boss, but you should be fine if you stay on the move. When he starts launching homing fireballs into the air, run away and focus on dodging them. When he isn’t doing that, hit him with as many long range moves as you can and stay far, far away. He has a conical flame blast which you can’t avoid, no matter how fast you are, so the best strategy here is to stay out of reach and stay near/in water.
Kassuq, the ice king: The toughest fight in the dungeon by a large margin. He’ll alternate between firing waterballs and ice balls at you. The waterball travels slowly and when it hits you, it will surround you with a sphere of water. Avoid this by moving away from it: it moves barely any faster than a crouching player so this should be pretty easy.
When he fires an iceball at you, just let it hit you and stand in the center of the ball, or it’ll start suffocating you. Alternatively, if you can time it right, you can deflect this move with a well placed shield. It is impossible to dodge this move, since it moves way faster than you can and has perfect tracking.
He’ll sometimes stand still and surround himself in a ring of ice and water, which will deal constant damage to anyone within it and pull them toward him. Just run away: don’t try to hit him or deal damage, just run when he does this or you’ll die.
He will also periodically create ice mines. They’re pretty dangerous, so just make sure you keep track of where you’re standing.
Tashi, the last airbender: This guy will shift between two forms through his fight. In turret form he’ll hover in the air and fire air bolts at you constantly. Just side step these and use this as an opportunity to heal. You can also deal some damage if you’re confident in your ability to avoid his attacks, but I don’t recommend trying. When he exits this form he’ll temporarily stop firing projectiles and you will be surrounded by air particles. When this happens, jump into a pool of water or you’ll be thrown into the air and take a ton of fall damage.
Tashi, upon leaving turret form, will run after you and deal loads of close range damage, periodically releasing explosions of air centered on his person. Stand in water when this happens and hit him with everything you’ve got: you can’t outrun him, he just moves too quickly. This whole fight is a battle of attrition, one which you should be able to come out on top of if you play it smart.
Ciquk, the waterbending arsenal: This guy is straightforward. He throws spears, bolts and tentacles at you the whole time that you’re fighting, dealing a lot of constant damage. Don’t stand near the pools of water, as appendages made of water will periodically come out of them and hit you if you’re nearby.
Ciquk will sometimes pull you toward him with a water tentacle. When this happens, don’t panic. Use a mobility move to avoid the fall damage, deal some damage to him, then run out of the range of his pulls, which have a slightly shorter reach than his projectile attacks. He’ll sometimes surround himself in an aura of water particles which will slow you down if you stand within them. This isn’t very dangerous, however.
The key to this fight is using shields and your environment to block his attacks while dealing damage to him faster than he can do it to you. It’s basically impossible to avoid taking damage during this fight, so just focus on killing him before he can kill you.