The Armchair Empire has conducted an interview with Stormfront Studios' Alyssa Finley, in which the Forgotten Realms: Demon Stone producer discusses various aspects of the Dungeons & Dragons console title. Check it out:
Q: On-the-fly character switching is one of Demon Stone's features. How is this being implemented? Can you provide an example of the feature in a game situation?
A: Basically, at almost any point in the game, you can make a strategic choice about which character of your party to play. Each character has different strengths, and based on the situation and your playing style, you can choose a different person to control. Rannek, the Fighter's strength is in melee combat: hitting multiple enemies with one attack. The Rogue, Zhai, can kill enemies in a single attack using her stealth backstab, and she has jump and jump attacks in her arsenal as well. And Illius, the Sorcerer, has unlimited ranged attacks, and can upgrade to more and more powerful spells during the course of the game.
As an example of switching gameplay, in the Jungles of Chult, the party travels on a raft for a while. They're being attacked from the shores by ranged attackers, as well by enemies climbing onto the raft. The player can choose to play the sorcerer Illius, to wipe out the guys on the shore or they can play Rannek or Zhai to take on the monsters in hand-to-hand combat. The system controls the characters you don't choose to control at any moment.
Another good example of switching on the fly is that you can cast a sleep spell on enemies with Illius, and while he's still in the middle of the spell casting you can switch to Rannek or Zhai and launch an attack on the immobile enemies just as Illius' spell takes effect.