When Rainbow Six Siege was first shown off at E3 2014, it seemed like another run of the mill modern day military shooter from Ubisoft, at least from a thematic standpoint. Yet, almost half a decade later, there are now space-based parasitic zombies in a game that prides itself on being reasonably realistic. Thanks to the Operation Chimera update and the associated Outbreak event, you too can shoot fast zombies, big zombies, exploding zombies, and magical zombies in a game that you would've likely never expected zombies to show up in at all.
While Outbreak may be a rather unexpected change of pace for Rainbow Six Siege, at the end of the day the only thing that matters is the one question that permeates all of gaming: is it fun? Conceptually, it's not redefining the wheel, especially if you've played Left 4 Dead before. You and two other people have to make your way through a map that is infested with zombies while completing a few objectives along the way. Zombies appear to spawn randomly, meaning that you can run into a Smasher (Outbreak's Tank analog) during one encounter while at other times the Smasher may be replaced by an Apex, what is effectively a magical zombie that spawns other zombies. The objectives in Outbreak aren't particularly out of the ordinary, usually boiling down to defending a room while zombies rush you. Occasionally you have to escort, or perhaps more accurately, carry an NPC from one point to another, though you can always drop the NPC if you really want to blast away with your primary weapon. Supplies are scattered around the map (good news if you can't play with friends), but for the most part, you and your team are on your own.
All that being said, Outbreak does have some merit. The three linear levels feature dark and infected locales that are, like Siege's take on space-born parasitic zombies, quite beautiful in their own way, but once again, they're nothing out of the ordinary. From a gameplay perspective, it is a nice touch that not all the objectives are marked, presumably to encourage teamwork and exploration, but this can conceivably lead to some frustration if your teammates are less than cooperative. Thanks to Rainbow Six Siege's preexisting gameplay mechanics, combat is very enjoyable, if a bit hectic (seeing as how the main game revolves around comparatively small scale and quick firefights, this should be expected). This is doubly true when you are tasked with defending a room, as Siege's unique environmental fortification and destruction mechanics give you some control over where the zombies come from while at the same time giving the zombies a means to surprise players. Needless to say, it is not a pleasant sight to see zombie limbs stabbing through a door barricade or a wall that you forgot to reinforce, but it is very thematic.
Purists would likely scoff at Outbreak and its decidedly unrealistic premise, but everyone else might like it due to the sheer simplicity of the mode. Ultimately, Outbreak is purely a "for fun" mode that Rainbow Six Siege desperately lacked before, and the fact that Siege's core mechanics are apparently quite apt for zombie killing is good news if Ubisoft decides to pursue similar projects in the future. That Outbreak is the only update for Siege that features any kind of noteworthy character development- with four cutscenes and a fair amount of in game dialogue no less- is refreshing, if a bit annoying considering how interesting a single player/campaign mode could've been (if highly impractical, all things considered). Like the zombie theme as a whole, Outbreak is nothing special, with no particularly amazing or noteworthy moments that are unique to the gamemode, but if you don't go in with exceedingly high expectations, then chances are that so long as you enjoy Siege, you will enjoy Outbreak.