Tatsu Tatsu no Mi, Model: Zmey Gorynych

Introduction
The Devil Fruit was discovered by Karas during the time skip however, he decided no to take it until his brother's death when he took it to gain as much power as possible to defeat Akainu

Appearance
The Fruit is a dark blue pear

Weaknesses
Normal Devil Fruit Weaknesses

Also the user needs to eat a lot in this form to keep their energy up to stay in this form