Hit the showers, Thunder
Like Jago, Sabrewulf, and Thunder before her, Orchid is the new free playable character for Double Helix's Killer Instinct. As the trend has gone recently, she'll probably only be available for a week, at which point another fighter will get the call to take temporary control of the spotlight.
If you're not the type to stay commited to characters for one week at a time (which I'm sure Microsoft is banking on), they're available permanently for $4.99 a piece or $19.99 for the entire season's cast. Spinal was added just last week, and it has to be damn near impossible to kill something that's already dead.