??? is a temporary perk that affects both explorers and companions. It is granted only when a player enters a Portal location into a Portal World. It lasts for a random duration between 20-30 days of travel (resting does not affect its tick).
After it's countdown is complete, it will automatically expire and transport the group back to the portal location on the original map. It can disappear prematurely if the player chooses to return to the original map by going back through the portal early.
It can be extended by another 20-30 days if the player has a Metal Cube in their inventory. Metal cubes are automatically consumed to grant this extension, and multiple cubes can be used consecutively to allow the group even 100+ days in the world.