After defeating the welcome party, press on any of the two narrow pillars on either side of the step to enter the circular room and travel down the corridor behind the two doors at the other side to reach a ledge. Watch out for the fireball shooter that activates behind you.
Jump onto the central island of the swamp. Note the ledge with the Falcon Shield to your left and also the wooden pillar.
Falling will mean losing a little health and battling the Stalkers. You can get out of the swamp using a lift on the right side of the structure that takes you back up to the ledge. If you are playing as the Mage, you can find the second segment (the only one on the hub) of your fourth weapon down the left side of this ledge.
Have a look around the edges of the right side of the island from your vantage point to see a series of steps going down (they aren't shown on the map). They lead to a small cave under the main island. Press the switch inside this small cave to light the brazier on the surface of the island.
Now you have to jump down into the swamp and use the above mentioned lift. Return to the circular room to find the central pillar has risen to reveal a bell. Hit the bell with any of your weapons and the vibrations will make the wall to the right of the bell explode revealing a new passage way that leads around the right side of the swamp.
On the way down this passage you'll pass an opening on the right leading to a small room with a teleporter at the end. Enter said teleporter, while watching out for the fireball shooter that activates behind you.
You will appear in a small brick enclosure. Press use on any of the sides to lower the walls revealing that you are in the middle of a courtyard surrounded by many Chaos Serpents. Battle them and afterwards head north and up the stairs to the ledge with the Falcon Shield on, seen earlier. Moving onto said ledge will spawn a magic bridge in front of you leading to the central island as well as several Chaos Serpents. The wooden pillar on the island will start moving up and down like a lift.
Jump on it to be taken up to a small cave in which you'll find the map's planet. Return to Hub 1: Blight (map).