SAD

SAD is a substance produced in a lab within Punk Hazard, D Block, and kept within a huge metal vat.

It was first alluded to in a conversation by Vergo, before being revealed to be Trafalgar Law's true objective on Punk Hazard.

Appearance
When it was first seen, SAD was being kept in a large metallic vat hooked up to several tubes and a prominent nuclear symbol on it. After the vat holding the refined SAD was split open by Law, the substance is revealed to be somewhat of a foamy mixture similar to wax.

Properties
SAD is a particularly unique substance and it is one of the few things needed to create Smiles, artificial Zoan Devil Fruits. It has the potential to cause anarchy within the New World, depending on the one who wields it. It also might have some radioactive properties, as the symbol for radioactive substances appeared on the tank Law was looking at; and Law himself noted that the laboratory will soon explode after the state he left the SAD production room in.

Caesar Clown is the only person in the world who knows how to manufacture this substance, and he created it by making practical application of Vegapunk's discovery of "lineage factor". As such, SAD is very valuable, as Donquixote Doflamingo suggested destroying the production room and eliminating Caesar to prevent it from being stolen and the scientist from being kidnapped, only to retract the suggestion as it would be troublesome for him to lose his supply of the substance as well as any chance of procuring more.

Punk Hazard Arc
Vergo arrived on Punk Hazard shortly after catching a ride on a SAD tanker ship that was leaving from Dressrosa.

Trafalgar Law apparently went through great lengths to gain access to the SAD production room on Punk Hazard, joining the Shichibukai and then forming an alliance with the Straw Hat Pirates. He eventually succeeded amidst the chaos in the research facility, but Vergo contacted Doflamingo and reported it. Vergo was ordered to stop Law from taking the SAD and execute him for his betrayal, which leads to the two of them battling in the production room.

After Law and Smoker engaged and defeated Vergo, Law broke the production machines, crippling the production of SAD. Due to this, afterwards the entire room explodes with Vergo inside of it.