Stuck @ Amazonia

[J.B.]

You need to help Queen Diana first with her questline. Then you will get some quests related to her three daughters. One of them will lead you to a garden area on Amazonia which is guarded by Silva, the Amazone. She won't let you pass until you have the relevant part of the "Diana & her Daughters"-Quests. If you have the permission to go there, you'll have to fight Silva once (like you do with Marina) before you can enter the garden area (iirc).

Good Luck

J.B.