What it does

"Modifies a Corrupted Equipment or Jewel item unpredictably or destroys it." It is one of the few things that can still change an item after a Vaal Orb has corrupted it.

The risk

There are two outcomes: a further change to the corrupted item, or losing the item outright. Use it on something you could replace.

Where it comes from

It comes from Atziri's Temple, which became a permanent part of the game in patch 0.5.0.