The Origin of the Slith

This is an Act 1 side quest offered by Kasparov after completing the Dangerous Curiosity quest and gaining Honored status with Devil's Crossing

He asks you to travel to Hargate's Isle and recover the notes of the scientist Oswald Hargate.

Objectives

 * Recover Hargate's Formula
 * Bring the Formula to Kasparov in Devil's Crossing

Guide
The isle is reached by boat. A Row Boat can be found just outside Devil's Crossing; after crossing the bridge turn left and follow the water-line until you reach it. Clicking on the boat will teleport you to Hargate's Isle.

At the north of the island is an abandoned house with a Trap Door that leads to Hargate's Laboratory. The formula can be found in an Ornate Strongbox at the end of Floor 2.

On returning to Kasparov you can then choose to hand over the formula or keep it for yourself.

Keeping the Formula unlocks another sidequest in Act 6, Hargate's Mysteries. Returning the Formula will unlock the Kasparov's Gamble sidequest in Act 6

Rewards
If you give Kasparov the formula:

If you refuse to hand it over: