To discover Garden Sanctuary, also known as treasure island (TI), you will have to complete a map composed of 3 different pieces.

The first piece (right part) can be found at Ibod, in Caravan Way. Talk to him, again and again, till he has it. He will sell it to you for 500 CPs.

The second piece (central part) is own by Keli, the insane guy that you will find downstairs Clockwork island 2. Talk with him and he will give it to you as you want to leave.

The third part (left part) is harder to get.You will need to meet Zydeko the lizard, in Altaruk. Play with him to his stupid game, Elements and Influences. You will have to win a first play before you can really chat with him. Then he will propose you to gain the map part if you can defeat him several time. I had to defeat him 11 times (plus the initial defeat to talk with him, that makes 12 at all), but maybe there is a random factor on the number of victories you must take. You can find here some tips that will help you to win versus that damn lizard.

When you have the map, call a friend and let him JOIN you, talk to Larak and he will propose you to go immediately to Treasure Island. Be careful when you have the map, you will loose it if you go either to TI or Cromlin, and complete the quest (s). If you go and don't complete the quests, you keep the map normally. So as you need to be at least 2 to complete TI's quest, manage that the one who has the map doesn't do the quest...

Fortunately, if you loose the map, you will regain the left part with only one victory vs Zydeko. You will just have to harrass Ibod and Keli again to get the other parts.