This has happened to me twice now. I'll help someone throughout the entire area (ex. Sen's Fortress) and then when we get to the boss they'll banish me from their world. Like what the heck man? *** pisses me off. I carried you through the ENTIRE fortress, helped you get all items, and then you banish me?
Don't play with Purple Anomaly, he'll let you carry him through an area and then banish you.