Toriyama and Kitase have been interviewed by Dengeki Playstation, in which they reveal a few new details about DLC and how Monsters play out in your party in Final Fantasy XIII-2.

So far, a fair amount of DLC has been announced. Kitase tells Dengeki that we can expect a lot more with downloads coming out about twice a month after the games released. He does however say that it won’t be as simple as just downloading an item or costume. To unlock them, you have to clear certain requirements within the game, such as defeating a particular monster. Right now, they’re making the necessary adjustments to the game to make it so the downloadable costumes will be visible in cutscenes.

Dengeki has gives a detailed explanation of the games Summon Raid and Syncro Drive Gauge systems used by Monster party members.

Summon Raid

Some Monsters turn into crystal during battles. The amount that do is dependent on the Monster. You can set up three monsters for use with Summon Raid, each with different roles in combat. When the player switches Paradigm, the monster with the role best suited for it will be swapped in.

Syncro Drive Gauge

When a Monster is fighting with your party, it builds up the Syncro Gauge. When the Gauge is full, the Monster has the chance to perform a special move. It may involve the player performing quick-times.

Source: Andriasang