Once the door is closed, there's no way to open it, as the doorway seems to disappear.

Once both of them are inside, the hallway walls turn into what looks like poison. However, there's no poison in the air or and the walls continue to feel the same as before.

There are three paths to choose from. One going forward with nothing implicating what might be in that direction, one going left (has a potion bottle motif in stuck in the wall as a sign) and one going right (has the same shield motif that was on the original door, stuck in the wall as a sign).

Which path are they taking?