Raid Mode contains about 40 levels, all pulled from the single player content. The gameplay is tuned to be a little faster and more action-oriented than the campaign, and a large number of monsters are around every turn, some with extra abilities or buffed defenses to make life hard for you. Each level can be completed in about 5 to 20 minutes, which jives well with the portable nature of the system. You’re also able to select from a stable of characters, each with different weapon proficiencies, level them up, and equip them as you choose.
Raid Mode has its own item shop, where you can buy new weapons, modifications or ammunition for your characters. Currency for this store is earned when completing chapters in the campaign and performing well in Raid Mode sessions. As an added bonus, there are a few items you can even purchase using 3DS Play Coins (you know, the currency used in Find Mii and Puzzle Swap).
You can bring a friend along to play Raid Mode, provided you know someone with a 3DS or are sitting within range of a Wi-Fi connection. Setting up a co-op session is a snap, letting you poll your 3DS friends list or using the simple filtering system Revelations offers for finding open games over the internet. If you’re the patient type, you can simply open up a lobby and allow players to find you. You can also play solo if you prefer, but I think you might be on the wrong site if that’s your cup of tea.
While playing in co-op, I didn’t notice an appreciable difference in difficulty, other than the levels becoming a lot easier due to the added firepower. You can, however, metagame around this by using certain weapon mods that have added effects. There are mods that increase or decrease the amount of threat (to borrow the MMO term) your weapons generate, and mixing a high chance to stun in with these things can really change how you’d play.