Ishi Ishi no Mi

The Ishi Ishi no Mi is a Paramecia-type Devil Fruit that allows the user to absorb, manipulate and merge with stone, making the user a Stone Assimilation Human (岩石同化人間). "Ishi" (石) means "stone" in Japanese. It was eaten by Pica.

Strengths and Weaknesses
The Devil Fruit's primary ability is the power to merge and assimilate with stone or earth. This allows the user to take control of anything made of earth that they come in contact with. In Pica's case, he can control Donquixote Doflamingo's castle as if it were his own body, as it is entirely made of stone.

Aside from the standard Devil Fruit weaknesses, this ability currently has no other known vulnerabilities.

Usage
Pica can use this ability to merge with any earthly substance, hiding himself and taking complete control of the area as it were an extension of his own body. He took complete control of Doflamingo's palace, which is made entirely of stone, causing the hallways to close together.