You need to talk to Pothos to learn how to get to Mad Mage Isle. Go East from Rotoluncia's House the Coast along to a Dock. On the way to it you will meet an evil Dark Monk and a Ranger and at the Camp is 8 Guilders lying around and in the Chest are some Reagents. South of the Dock lives a nude Woman who won't talk to you. Click on the Bell to call the Turtle who bring you to the Isle.
In the Crate is a Stop Storm Scroll. In another Crate by Vasel's Bed is Deter Scroll and Flash Scroll. The Scroll on the Table explains what happened with Boydon which is now a living Head lying on another Table. There is one more Scroll (Erstam's Surprise) in the locked Chest. The Telescope will show you where the Magebane Sword is. Now talk with Erstam and tell him the Password. Then talk with Vasel about Teleportion and talk again with Erstam about it. Agree to help him to find a Phoenix Egg. He will then send you to the Isle immediately.
Upon the Arrival you will be greeted by Wildmen. Go North until you see some Mushrooms. Behind it is 2 Potions. Go East and exit South. The North Path only leads to more Wildmen who protects a measly 3 Monetari. Follow the Path around to another Cave Entrance. Enter it and go East to a small Room with a dead Bird on a small Island surrounded by Lava.
Pull the Lever to revive the Phoenix. You will receive the Phoenix Egg. Go South and West and step on the Teleport-Pad to teleport back to Mad Mage Island. Talk with Erstam again and help him collecting Body Parts and put them in the Machine. You need 2 Arms, 2 Legs, Head (Boydon) and Torso (is in Crate). But only the unmoving Parts should be taken the other which move will not work. Lastly put the Phoenix Egg in the Machine. You see a Boydon with all his Body Parts put together.
Erstam will then give you a Blue-Red Key and the first Serpent Tooth (actually the second if you took one from Rotoluncia's House), this one leads to the Mad Mage Isle. Now go to the Warehouse and unlock the Door. Get the Jawbone and 2 Mana Potions from there. Go back and talk with Erstam again. He will give you two more Serpent Teeth. One leads back to Moonshade and the other leads to Monk Isle. You can view the Jawbone with . Be sure to drop all Serpent Tooth on the Jawbone or the corresponding Gate on Dark Path won't open for you.
If you want, you can also recruit Boydon to travel with you. He has 30 Strength so he will be a great Pack Mule, but the downside is that if he die he can't be revived. Go back to the Warehouse again and doubleclick on the Serpent Gate in there. If you have the Dark Path Map, then know that you are in the Middle and Furnace ( Tooth from Rotoluncia's House), Moonshade and Mad Mage Isle are on the West Path while Monk Isle are on East Path.
Visit the Furnace first and get 3 Magic Scrolls off from a Corpse near the Gate. It's Columna's Intuition, Unlock Magic and Fire Field. Go back to Dark Path. Your next Goal is the Monk Isle and this is where we will be going.
Talk with Erstam about Teleportation Storm and he will eventually tell you that a Dagger which got swapped in the Storm is lying around in the Manor. You can pick it up behind the Stairs. The Dagger got swapped with the Severed Hand of which you can now drop.