At first glance, the most striking thing about this potion is the bottle; where a normal potion bottle is either stout glass or reinforced by a metal frame, the bottle of a rubberized shadow potion is crafted from pitch black steel.  Not that you can tell from looking at it, as the potion within will have altered the look of the steel to a shade so dark as to seem like a void in space.

The bottle is quite safe to handle, however.  It can be opened by popping the cork (you have to feel for it, since you can barely tell by its silhouette).  The magic happens by pouring the contents onto an existing bit of shadow.  The thick ichor pours with surprising ease, spreading to fill the area the shadow falls – up, down, and around corners – where ever the shadow covers.  A single flask of rubberized shadow contains enough shadow substance to fill an area of 100 square feet.  If the size of the shadow exceeds this limit, the ichor won’t pour at all.  In the event of multiple overlapping shadows, the ichor will only affect the most prominent one.

Once the ichor has filled in the full area of the shadow, it becomes reactive to other shadows.  Further, any action performed against the shadow will have a like effect upon the object which cast it.  The rubbery nature of the ichor applies to the affected shadow, giving it a springy, flexible nature.  This new malleability translates to the object as well.  By pushing or compressing the shadow, the object will likewise deform, within limits.  Softer objects can be bent out of shape with much greater ease than harder objects, so a person would compress after much less exertion than a brick wall.  The object will bounce back to its normal shape as soon as the pressure is relieved.  Note that this compression does not damage or harm the object in any way – at best, it will limit mobility or functionality.  Only the individual who poured the rubberized shadow can manipulate the shadow ensorcelled by this brew.