Schweizer I think no-one here is going to tell you the exact exercise you're gonna get... not out of fear of competition, but out of decency and unwillingness to destroy a potential future job offer. The employer expects candidates not to share confidential information and breaching that is not something one should even consider. Even if that was not enough reason, it would be very suspicious if you showed up knowing exactly what is going to happen.
HOWEVER
having said that, the phrase 'prepare as you believe is adequate' goes a long way... you already know that it involves a group exercise and panel interview, and a lot of information about these kind of assessments can be found online.
and having said THAT: the assessment is about your personality and wether you will fit in with the company, for a psychological assessment there is not much to prepare for. Naturally you should prepare for the interview, and for that there are also many good sources online to guide you in your preparation.
Bottom line: if the assessor sees you as someone who will fit in with the company, they will pass you. Show teamwork, help others perform well, and never ever try to bull**** your way through a question you dont know the answer to. Because they do know the answer and you will just look like an idiot.
Best of luck!