The Rings of Power season 3 introduces a new wizard who showrunners J.D. Payne and Patrick McKay hinted in 2024 is actually one of the two Blue Wizards from Tolkien's lore. The Dark Wizard, located in Rhûn, seeks to usurp Sauron and poses a threat to the Stranger, revealed to be Gandalf, who trains with Tom Bombadil at the end of season 2 to prepare for this rivalry.
The Blue Wizard has already demonstrated significant power through both magic and allies. He seeks to usurp Sauron, placing his strength well above Gandalf's current level. Since Gandalf remains with Tom Bombadil when season 3 begins, the Blue Wizard will still be stronger than him at the series' return.
His power appears to fall somewhere between Gandalf and Saruman at their peak in The Fellowship of the Ring. The show implies he hasn't revealed his full strength yet. Gandalf the White, who gained immense power in the later films, likely surpasses him.
Season 3 is setting up a battle between Gandalf and the Blue Wizard. This diverges from Tolkien's canon. According to Middle-earth writings, the Blue Wizards explored the Eastern part of the realm but had no recorded conflict with other Istari. A conflict between Gandalf and the Blue Wizard creates a rift among the Istari absent from the source material.