Stuck With Beneath The Depths (quest) Any Tips?

Hey guys, I have been recently been playing Wynncraft, and I have zoomed past every quest possible (except TOA), and found myself stuck in the Beneath the Depths quest, this quest was a pain in the but. It took me a week to finish all of it, except the boss, it is really annoying. That is why I posted this, I needed tips to complete it, or friends (I HAVE NO FRIENDS D:) to help me finish this, because I really want to beat this quest, and finish with this annoying Pirate Cove things (NO HATE)! I just need tips for now, as I have already found a friend to do it with. I am the same LVL to start this quest, and am an Assassin class. Please help me with this quest as it is really difficult and repeatedly die, which means repeatedly swimming back all the way there, and having to find out you die again. Even boats are a pain, 2 EB, is way too much, and then it disappears sometimes, I wasted 34 EB total, by this quest, by spending money on boats, health pots, when they all run out or disappear, have to buy them again and again. So now I have only 65 LE, which is poor.
So please help me with this quest by giving tips.

 

Um... Losing 34 Emerald blocks out of 65 LE is like lost 1/128th of your entire balance....
I have 58 Le, and I have been playing Wynn for 3 years.

Anyways, I am guessing that if you cannot beat the boss on your own the only alternitive is either to get a better build, or get some other people to help you out with it.

Proper sections to post this in:
To Ask Questions: https://forums.wynncraft.com/forums/questions.89/
To get a class build: https://forums.wynncraft.com/forums/class-builds.100/
To Organize a party to kill The Treasure Guardian: https://forums.wynncraft.com/forums/the-planning-parlour.77/


In the Treasure Guardian's arena, there is a little building:

Lead him into the building and attack him through the wall.
That should garuntee his death.