For for the transparent shaman objects, see Ghosting.
For the skill, see Architect.

Ghosts were interactive moving characters appearing in Halloween 2012 event maps. If a mouse touched one of them, the mouse will lose one out of 4 health points. They can only be killed with the mouse's wand by swiping at it for about 4 times. The ghosts also appeared in Grim's Mansion as a traced version but did not harm the mice in any way.