How do I enter the Akadai underworld?

[Lysippe]

I had decided not to kill and decapitate the chief Akadai. I have not been able to find an entrance to the underworld. Just in case killing him was necessary, I have experimented after saving the game right before I enter his compound. Killing him does not reveal an entrance. Killing his guards does not either. Where is the entrance? Do I have to kill him or is there another way to enter?

[KillingMoon]

[+] SPOILER

If you have the quest 'Finding Another Way' in your quest book (I'm not sure about what happens when you've opted to go for his scalp), you should have been given the option to tell the Akadai kingspawn you're looking for a Crux stone. He will then offer you a gland, which is the key to their underworld.

Also in a chest behind him is a gland, so that's another way to gain entrance, one that doesn't involve the need of a dialogue.

[Lysippe]

Actually, I did get that gland from him. It has not revealed anything, however.

[KillingMoon]

You may not have explored everywhere. The entrance is a very recognisable landmark, somewhere in the south-west of the island. It's interactive, I mean it lights up when you mouse over it. Really hard to miss.

[Lysippe]

Got in! Thanks! The only problem I'm having down there is that gate that doesn't seem to open and the three oyster shells, but eventually ....