The Master wand is the strongest of the wands, requiring a very high skill in Magic to wield. It can be obtained by either exchanging pizazz points at the Mage Training Arena or buying one from another person.
The first mention of a Master wand in the novels was in While Guthix Sleeps. King Roald uses his wand to conjure a rope, as well as a pointy rock, onto which he tied the rope. He had conjured the rope in order to get down into the God Wars Dungeons to obtain the Zamorak god shard.
The wand doesn't seem to appear again until the next book, Through the Eyes of Guthix. King Roald's Master wand was confiscated by the bald man upon being imprisoned in the Woods of Holly Prison. He eventually got his wand back, as him, Aidan Knight, and Ezra escaped. They came into an encounter with Zamorak. Zamorak casted Vengeance upon Roald, but Roald destroyed the skull with his wand, although cracking it down the middle from the intensity. Sometime between when he and Aidan fell asleep in the Asgarnian Woods on Christmas Eve and Christmas morning, Roald went to visit "an old mage", who helped repair Roald's wand.
Roald uses this wand again during the Battle in Canifis, duelling with Simivance. It is revealed that Mr. Simivance also possesses a Master wand.