In time line, Killzone 2 follows Killzone: Liberation, and Killzone, and appears to take place entirely on Helghan, the home-world of the Helghast who invaded an Interstellar Strategic Alliance (ISA) colony in previous Killzone installments. Two years after the Helghast assault on Vekta, the ISA is taking the fight to the enemy's home world of Helghan. The ISA goal is direct: capture the Helghast leader, Emperor Visari, and bring the Helghast war machine to a halt. Assuming the role of Sev, a battle-hardened veteran and a member of the special forces unit known as the Legion, players will lead a group of highly trained soldiers on a mission to take out the Helghast threat. For Sev and his squad, the invasion of Helghan is just the beginning. During the invasion of Helghan, Sev's unit is deployed behind enemy lines to assist the main invasion force. Tasked with securing Pyrrhus, the Capital City, the team quickly discovers that the Helghast are a formidable enemy on their home planet. Not only have they adjusted to the planet's hostile conditions, they have also harnessed a source of power they can now use against the ISA - the frightening ability to control surgical lightning storms. Sev discovers his squad is not just fighting enemy forces – their fiercest opponent may be the planet itself.