Ubisoft has launched the first big piece of content for Year 3 of Tom Clancy’s Rainbow Six: Siege today. The update, called Operation Chimera, introduces the cooperative horde mode Outbreak as well as new operators Finka and Lion. You can download the patch right now on PC or consoles, and it includes a number of bug fixes and game tweaks in addition to the new content.

The publisher has turned Rainbow Six: Siege into a massive success in the time since it launched near the end of 2015. It has done that through regular updates to shore up the core gameplay, but also through consistent content patches that introduce new characters and cosmetics. Ubisoft is shifting to a live services model, and Siege is the best example of that with its 25 million players.

Outbreak is reminiscent of other cooperative horde modes like Call of Duty’s Zombies where you set up defenses and shoot incoming, mindless attackers. But Outbreak also has elements from Valve’s Left 4 Dead as it has the squad of players moving from one position to another in a level after clearing out a swarm.

The cooperative event is free for everyone, and it runs through April 3.

The two new operators are attackers called Finka and Lion. They are only available for people who paid $30 for Siege’s Year 3 Pass, but they will launch for everyone else beginning March 13. At that time, you can purchase them with in-game currency.

Finka is a support-style character who can heal everyone on the team for 40 HP up to 3 times per match with the push of a button. This ultimate gadget also gives players steadier aim and revives teammates who are down-but-not-out.

Lion provides extra tactical information through his gadget that can see people through walls as long as they are moving. This is the kind of thing that you’ll want to pair up with other characters’ abilities to get the most out of, but it can help you wipe out the last couple of opponents during a round if you use it at the right time.

This is just the first season of content in Year 3 of Siege content. Before this season pass is through, Ubisoft will launch 6 more characters, 2 new maps, and a rework of an existing map. For now, however, it’s time to learn how to use Lion and Finka effectively and kill zombies.