Isk
The Isk are one-half of the species called the Iskoort in the fictional Animorphs books by K. A. Applegate. They are the physical bodies built to house the Yoort, which are slug-like creatures similar to the Yeerk. Unlike the Yeerks, however, the Isk and the Yoort are symbiotes. They are slightly shorter than humans, and have roughly triangular heads.
ISK is also the name given to the monetary units in EVE Online. EVE Online is a massive multiplayer online game developed and owned by CCP Games, Iceland.