The Haven Isle

Every time you enter a multiplayer game you will start out on the Haven Isle (which is added to your Main Portal options). Also anytime you die in multiplayer (unless you are playing Hardcore) you will be brought back to the Haven Isle. On Haven Isle is a Merchant, Blacksmith and Combo Master that you can access immediately upon entering the game for your convenience, there is also your stash box in the center of the island. Lastly the island has three portals and a tower. The portal on the left will bring you to the center of Bellevue, the portal on the right will bring you to exact location you died if you have died in this game. If you haven't died it will just pop you back to the center of the island. The portal on the far, far right of the island will bring you to the very beginning location of the Underworld Main Campaign. The tower leads downstairs to a portal room, the location that each room brings you is marked below:

If you speak to the goblin who is standing in the center of the Portal Room he will give you a warning:

As Anur says... THESE ARE ONE WAY PORTALS! Once you enter one you cannot come back to The Haven Isle without walking to a Main Portal. If you would like to see exactly where the portals in the portal room drop you, see the Portal Room tutorial.