The Netherverse is the dimension where the Nethers live. They are ruled by Mr. Eye. The barriers between dimensions was weakened when the Fongoids caused a hiccup in the space-time continuum, this was later exploited by Mr.Eye and Vendra.
In the background of the Netherverse, especially during Clank's fourth trip into the dimension, one can see buildings in the background. This implies that the Nethers have a prominent civilization, just like the lombaxes.