Tuchanka

Tuchanka is the homeworld of the krogan race. When the krogan entered the nuclear age in about 1900 BCE, they began using nuclear weapons in their frequent civil wars. The result unleashed a nuclear winter on Tuchanka, and reduced the krogan to primitive, warring tribal bands. This planet was also the home to the predators known as varren.

Even before its nuclear devastation, Tuchanka was notorious for its harsh environment with extreme temperatures, vicious predators, and scarcity of resources. This means Tuchanka's native species are usually adaptable, consummate survivors with fast breeding cycles to replenish their numbers.

According to the Mass Effect 2 website the player will visit Tuchanka to rescue a captured salarian scientist.

Trivia

 * The background behind Shepard is in fact Tuchanka.
 * The official website lists Tuchanka as being part of the Krogan DMZ.