Oath

"This… this…" Billy couldn't help himself, this was so strange... and so cool!

  he asked excitedly, "Can you tell me more about the oath tablet?"

Robin nodded, "The oath will stay active until the time limit in the oath is overdue, or when the tablet is destroyed. this is why I chose hard metal tablets as a medium so that they would not be easy to destroy with the passing of time and thus lose the imprint, but nevertheless, the tablets are still vulnerable to destruction if they fall into the hands of an average level knight, 

If a certain amount of damage is done to the tablet then the oath will be of no importance anymore... so I advise that after the completion of the oath swearing process hide the tablet In an extremely safe place, throw it into a sea or dig a hall in a mountain and throw it there... let it disappears forever.