Gandalf was a wizard from JRR Tolkien’s books, The Hobbit and the Lord of the Rings. Although he was initially known as Gandalf The Grey, he became known as Gandalf The White.
He bears one of the elven rings of power, called Narya, the Ring of Fire. It contains a red stone (presumably a ruby). The ring inspires others to resist tyranny, domination, and despair. We don’t know what metal it was made from. This ring comes from the poem:
Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men, doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them.
In the Land of Mordor where the Shadows lie.
Gandalf was NOT a ninja, which is a person trained in ancient Japanese martial arts and employed especially for espionage and assassinations.