Can you keep trying it in a full attack (or try it against different foes) more than once per turn?
This sentence starts out as fluff (since it is already covered by the weapon properties), but ends up as crunch with the stuff about mithril/silver.Furthermore, it strikes fearful blows with its first head against those of any alignment but Lawful Neutral or Neutral, and bypasses DR as though it were made of alchemical silver (but with no penalty to damage).