Mechanic - Two Worlds

As Marianne exists both in the real and spirit world, there are times when both versions of Marianne are controlled at the same time.

Some obstacles (like walls, doors, chasms, stairs, etc.) can exist in only one of the worlds. If you try to move through the obstacle while being in two worlds at the same time, a shadow of an obstacle
will materialize in a world where there is no obstacle. You won’t be able to go further
until you find a way to overcome the problem.