A commercially-packaged toy set containing a quart of viscous black “Shadow Paint” (SCP-1553-A), a white foam “Shadow Eraser” (SCP-1553-B), and a paintbrush. When the paint is applied to an illuminated surface and allowed to dry, the painted silhouette becomes an anomalous two-dimensional shadow object (SCP-1553-1); humanoid/animal silhouettes may animate as intelligent shadow entities (SCP-1553-2). The interaction field behaves like a physical object to touch, sound and motion, and its qualities are strongly influenced by the user’s intent and imagination. 

The Eraser neutralizes shadow instances on contact, but when used on the shadow of a real object or person, the erased region of the original will lose opacity and, within minutes, coherence and physical interaction—sometimes fatally in living subjects. SCP-1553’s effects scale with belief and intent, producing anything from flimsy toys to purposeful, dangerous silhouettes; for safety the Foundation limits instance duration and forbids persistent shadow activity. 

you find scp-1553 in your attic.