The Tale of the Remarkable Tool

Once, in a distant land, a great king received a traveller; a wandering knight and the knight told the King how he had travelled many hundreds of miles and, though encountering monsters and perils of all kinds, had managed to survive them because of a remarkable tool he possessed that could be whatever he needed when he needed it.
“What kind of a tool can do that?”, asked the king, eager to possess an implement of such enormous power, “Let me see it”.
“Oh, it is not a tool you can see, your majesty”, replied the knight, “But once, when I was facing a dragon with a hundred heads and had no other weapon, it became my sword and that dragon was struck down”.
“Well then”, said the king, “Let me feel the tool then”.
“But it is not a tool that you can feel majesty, at least, not with your hands; only with your heart”, explained the knight, “But once, when I was trapped in a dungeon by an ogre and had no other way of escaping, it became my key and I fled that dungeon and slew the ogre”.
The King was perplexed, “A tool that can be everything but which one cannot see and can feel only with one’s heart”, he said to himself, rubbing his chin.
Then the Knight, seeing that the King would never be able to solve the conundrum, revealed to him the name of his remarkable tool.
“It is my faith, Sire”, said the knight, “And no fiercer weapon nor greater tool was ever wrought from any metal upon this earth, nor shall it ever be. Whoever possesses a faith such as mine shall prevail over all and any circumstance”.