Warhammer 40K Conquest LCG: The Scourge War Pack - Rules of Play says:
The Scourge is the second War Pack in the Warlord cycle for Warhammer 40,000: Conquest! The Scourge continues to expand the main themes of the Warlord cycle with a new Chaos warlord and a host of new cards for every faction that interact directly with warlords.