Answer:
Belief.
Step-by-step explanation:
Belief is the act of thinking or attitude that what has been said is bound to be true or come true. It involves having faith or acceptance in thinking or expecting something to be true.
In the given condition, Robert holds on to the belief that the "medallion his mother gave him [will keep him] safe from harm". This means that he has full faith and accepted that he will be safe from any harm as long as the medallion is with him. This is an example of a belief.