You’ll be able to dress up your Avatar in COG Soldier and Locust armor. These probably aren’t going to be free, so start saving up your Microsoft Points. I’d imagine these would end up at 80 ...

COG Gear: General RAAM: Execute 30 COG characters as a Swarm character; The Coalition said it reckons it'll take around 10 hours to earn each character through gameplay, or faster "if you're good".