A mental and physical bond is a connection between two or more individuals, which means that they share thoughts and emotions, and are also strengthened when together.
This is a passive ability which cannot be consciously supressed, and which causes great pain and grief if it is blocked or negated. It creates a strong connection between the characters, which causes a sort of hive mind, where they can communicate telepathically and almost all thoughts and emotions are shared. The characters are stronger, faster and more skilled when together and in proximity, and it is almost physically painful for them to be separated. If one were to die, the others would be severely weakened and would be in great pain, and they could possibly also die if they were also weakened or injured. The ability also seems impossible to mimic or replicate.