Caduceus, Staff of Hermes, and With Great Power...

Prerequisites

• Caduceus, Staff of Hermes on the battlefield
• With Great Power
• on the battlefield

Steps

1. Whenever damage would be dealt to you, With Great Power
2. causes that damage to be redirected to the creature it is attached to
3. Since Caduceus grants an ability to the creature preventing damage being dealt to it, no damage is dealt to you or to that creature

Results

• Prevent all damage that would be dealt to you