How do I (re)visit the Gateway Island?

[Ungod]

I have my reasons to want to go back...

[Demonic God]

There are several methods:

• Via the Gazebo of Chaos. The method for which may be found in the Paper Cabin, and may require the assistance of other players
• By making use of jumps/teleports, if available. Note that this is rarely ever the case
• By being brought there by someone with the authority to do so
• By being given the authority/method to do so

[Miq]

It's not meant to be revisited but there is a puzzle that can be found in the paper cabin.

[Lazarus]

Like what Miq said. Other ways involve going to a certain place with other players and simultaneously activating a portal, and having a pebble to teleport oneself to the island.