The Dark Eco is a powerful substance in the Jak and Daxter series, and one of the two most powerful types of Eco. Dark Eco is often used by many villains in the Jak and Daxter universe.
Jak and Daxter: The Precursor Legacy
Jak 2: Renegade
In this game Jak is given the power to transform into a more monsterous form named Dark Jak due to being pumped full of Dark Eco. The primary villain Kor and his army of Metal Heads are also great manipulators of Dark Eco.
Jak 3: Wastelander
The most powerful practitioners and controllers of Dark Eco emerged, they are named the Dark Makers who are corrupted Precursors and are controlled by some unseen overlord. In the game, Erol appears as their leader, having gained the ability to manipulate and control Dark Eco.