Ge Chen's father mentions it first. He sends his son there to obtain the ritual that can bypass the Curse of Osiris which was placed on the Forbidden Sphere, making it mpossible for anyone to try to obtain the power of Set sealed there. The knowledge came from the Corpse Hand. But at first they have to gather the Sacred Weapons of the Camarilla in order to perform the ritual that can reveal the way to bypass the Curse.
Fraser, Lilla, Ge Chen and Yue Jian arrive there after managing to gather the weapons. Yue Jian got taken over by someone else, and she get them inside, otherwise they wouldn't have been able to open the door.
In the Ice Coffin Palace a woman was hidden and seemed to lay in deep sleep. She held the srcoll that was necessary in blocking the Curse of Osiris. The woman looked exactly like Yue Jian, Zhao Yan and Xi Yan.
It later turns out that she was Isis, the donor of the blood that was used to create the triplet. Either she was forced into a sleep and was sealed in the Ice Coffin Palace, or she chose it as a resting place while she was waiting for Set.
It is notable that place was full of the ice crystals that look exactly like the one Osiris casted when he fought against Zhao Yan and Fan Le Lao. And it is also similar to the depth of the Forbidden Sphere, were currently Isis and Set are residing, along with their prisoner, Yue Jian.