Jak and Daxter
A substance called "Eco" is also used by the people. It can be found as gas, liquid, or even solid crystals. There are several different kinds of Eco, and all the different Ecos can do special things. Green Eco can heal injuries or damage, and Blue Eco can make things move faster. There is also Dark Eco, a dangerous kind of Eco which can kill or mutate. In the first Jak and Daxter game, Jak and Daxter: The Precursor Legacy, the character Daxter falls into a pit full of Dark Eco and turns into an "Ottsel", a fictional, or not real, cross between an otter and a weasel.