A client reports that her husband has started talking at times in a foreign language, and at other times acts like he’s a different person. What is going on here?

This is spirit meddler mischief. They are playing with him. They are manipulating his thoughts and manipulating his mind, connecting him to their own idea of "fun" which is to perturb things. Anything they make him do out of context will cause problems for the host whether they recognize the odd behavior and are given a pushback from people around them or they see in retrospect there is something odd happening and begin to question their own sanity. It will stir things up, cause self-doubts, ramp up anxiety and fear, and this will bring in more energy the interlopers can siphon off for their own support. This is the primary motivation here rather than a higher-level manipulation or control for a nefarious purpose with a dark agenda as sometimes does happen. This is more generalized manipulation for simply stirring the pot to gain an energetic advantage.