Philosopher's Stone

The Philosopher's Stone is a new accessory item from 1.1 update. Dropped by Mimics

Trivia
Philosopher's Stone is a (possible) reference to Full Metal Alchemist.

Philosopher's Stone is a (possible) reference to Harry Potter [Unless you are american]

Philosopher's Stone is a (possible) reference to Indiana Jones

Philosopher's Stone is a (possible) reference to Valkyrie Profile

Philosoher's Stone may be a VERY DOUBTFUL reference to Touhou's Five Elements "Philosopher's Stone".

Philosopher's Stone is probably a reference to the Philosopher's Stone