The Echo Knight archetype of the fighter class has the ability to manifest an echo of the knight. This ability includes the following:
You can use a bonus action to magically manifest an echo of yourself in an unoccupied space you can see within 15 feet of you. This echo is a magical, translucent, gray image of you […]
On your turn, you can mentally command the echo to move up to 30 feet in any direction (no action required).
No limitations seem to be specified so does this mean that the echo can translate vertically (I hesitate to use the word fly or levitate) and/or though walls?