With all the keys in hand, you are finally ready to take on the big guy! Aren't you excited? Of course you are, because that's why you play these games, isn't it. Anyway, make your way back to the entrance of the Oculus. You will notice on the top floor that there is a blue crystal just sitting there. It is time to click on the crystal and unlock Ghaldrid's Chambers.

When you do enter his Chambers, make your way up the stairs until you see him, just standing there waiting for you. Talk to him and find out that he has been watching you this whole time, and is surprised that you have gotten this far. He feels that you still don't deserve his presence, and decides to let you face his wyvern, called Steng, instead. He summons Steng, who is a level 20 4dot mob. Killing Steng will prove to be little challenge, considering what it took you to get to this stage of the quest.
After you dispose of his Wyvern, he will finally fight you. He is a level 21 5dot mob, and should be around the same power as some of the headmasters, but about half way through the fight he will teleport away from you and reappear up on one of the platforms. He will also summon Redcaps and Fairies onto the platforms, which you will have to dispose of to get to him. They are all around level 20 and could be either 3dot or 4dot mobs.
Once you make it to Ghaldrid again, you will notice that he has gained all his health back. Once again, start killing Ghaldrid, or at least try to kill him. Again he will teleport up to the next platform. Now you will have to kill you way to Ghaldrid again, but this time, before engauging him, (*TIP*) keep going up the ramps until you reach the top of the platform, then kill the 2 mobs standing there, then head back to Ghaldrid and engage.
NOTE: During the fights on the platform Ghaldrid may knockback players, it is best to fight him in the middle of the platform so he doesn't knock you off. He may also teleport one of the members of your group out of the Oculus entirely, and place him on a small floating rock, with no way to get down. Do not worry if this happens, as after a bit, he will port that individual back into his chambers, and he will just have to run back up the platform to join his group members.

So I hope you listened to my TIP and killed the 2 guards, because if you missed out on killing them before you took on Ghaldrid the third time, you will notice that he is now cowering behind them. This will cause you to fight 3 mobs instead of 1, so my TIP is highly recommended.
If you did kill the 2 guards, then you will find Ghaldrid standing by himself on the top platform. This time you will be able to kill him (watch out for his knockback), as you watch him fall to his doom!

As you are looting him up, you will notice Titania appear out of thin air. She is the mysterious master of Ashby! She is happy at what you have done here today, and rewards you with your very own
Caged Redcap Brownie! This item allows you to summon a Redcap pet for 30 seconds to aid you in fights (has a 30 minute cooldown timer). She also offers you another gift, if you hand over all your keys to her. If you feel like you are never going to come back and do this event over again, then you can hand in the key, but if you want to come back, then refuse her offer and you can do the event whenever you want, without having to kill the headmaster again. (NOTE: the item she gives you will be soulbound, and may not be useable by your class).
Congratulations on completing this amazing dungeon, and good luck on your future adventures!