Portal Scroll

 is a consumable item.

Source
can be brewed in the Level 2 Alchemy workshop.

Use
can be used in the mines or in a dungeon to create a portal back to the player's workshops. The portal stays on the map indefinitely and can be used to go back to the dungeon anytime.

Only one one portal can be active at a time. Creating a new portal by using another Portal Scroll erases the old portal.