In Mass Effect 3 for the PC, PS3, and Xbox 360, you can unlock different races to use in multiplayer games.
Unlocking characters in Mass Effect 3 is similar to a CCG (collectible card game) in that you have to purchase packs with credits that you either earn from playing multiplayer games, or from buying them with real money.
There are three different packs that you can purchase with your credits, each with different odds of getting better cards.
Recruit Packs (5,000 Coins)
These are the basic entry level packs that contain mostly common and uncommon cards. You can get rares and ultra-rares from this pack, however it’s rumored that you can only get them after you’ve exhausted all of the common and uncommon cards first, so I wouldn’t suggest trying this for higher value cards. The recruit pack contains specific cards not in the other packs, being Rank 1 Ammo, Armor, and Weapon bonus items.
Veteran Packs (20,000 Coins)
These mid-level packs contain common, uncommon, and a chance at rare cards. This is probably your best bet for unlocking most of the different races in the game. The veteran pack contains specific cards not in the other packs, being Rank 2 Ammo, Armor, and Weapon bonus items.
Spectre Packs (60,000 Coins)
The most expensive packs you can buy, the Spectre pack contains common, uncommon, and a chance at both rare and ultra-rare cards. The spectre pack contains specific cards not in the other packs, being Rank 3 Ammo, Armor, and Weapon bonus items.
Unlockable Races from Card Packs
Here are the races you can unlock from card packs, and what rarity group they’re in.
Human Characters (Appearance Mods)