Rizon is one of the newer networks out there, and was founded in July 2002. Originally this IRC-network was founded to help users share copyrighted material since more and more of the larger networks had began banning users for sharing via their networks. Rizon turned around, and today its a regular irc-network and the administration now works actively to prohibit copyrighted material.
A write-up about Rizon’s history can be found here: http://en.wikipedia.org/wiki/Rizon
Underworld linked into Rizon in november 2006, and is currently hosting irc.rizon.no, irc.uworld.se and a hidden hub called underworld.hub.