Kahmunrah is the main antagonist of Night at the Museum: Battle of the Smithsonian. He is Ahkmenrah's older brother, who comes back to life and tries to use Ahkmenrah's magic Golden Tablet to take over the word, only to get thwarted by the hero Larry Daley.
He is portrayed by Hank Azaria.
Night at the Museum: Battle of the Smithsonian Edit
The story begins when Larry, now a wealthy inventor, learns that most of the exhibits of the American Museum of Natural History whom he befriended in the first film are being sent to the Smithsonian Institution to be replaced by holograms. He goes there to say goodbye to them and learns from Ahkmenrah that the Golden Tablet which makes the exhibits come to life is to stay with him in the Museum.
Alas, Dexter the monkey stole the tablet and brought it with him at Washington, causing all the exhibits there to come to life, including Kahmunrah's wax statue, who spends the night trying to take the Tablet from its crate not to avail. The tiny cowboy figure Jedediah manages to phone Larry to warn him, and Larry rushes there to get back the Tablet, guided on the phone by his son Nick.
Larry sneaks into the Smithsonian and tricks the night guard into calling sick, taking his keys and flashlight. He gets the Tablet from Dexter, but stumbles upon Kahmunrah, who has him surrounded by statues of his soldiers, demanding the Golden Tablet. Having seen too much during his time as a night guard, Larry is much less impressed as Kahmunrah would like to and talks back. Larry hands over the Tablet and tricks Kahmunrah into opening a crate containing a giant Cephalopod, stating that it contains a magic cube that obliterates anything standing in one's way. As Kahmunrah and his soldiers are being beat up, Larry takes back the Tablet and flees, pursued by his foe's guard.
During the ensuing chase, Larry befriends the wax statues of General Custer and Amelia Earhart, who help him get rid of Kahmunrah’s soldiers. Meanwhile, the evil pharaoh ransacks all the treasures of the museum, which he intends to turn into his new palace, before recruiting the wax statues of Al Capone and his gangsters, Ivan the Terrible and his soldiers, and Napoleon Bonaparte and his imperial guard. Oscar the Grouch and Darth Vader himself offer their services as well, but the evil pharaoh (wearing a bathing robe) dismisses the former for not being evil, and the latter for not having force powers, making his hand gestures sillier than threatening.
After an epic chase through the entire museum and inside the paintings of the nearby National Gallery of Art, Larry and Amelia are captured and brought before Kahmunrah. The evil pharaoh uses the Tablet as a keypad to open the Gates of the Underworld, but luckily the combination was changed. Kahmunrah captures Jedediah, who tried to sneak on him, and locks him into a filling hourglass, ordering Larry to find the new combination for him before sunrise, lest Jedediah dies smothered in sand.
Later, Kahmunrah sees Larry run of with the Tablet to get help from a window, and sends his men after him. Larry, who got the combination from Einstein bobbleheads, eventually returns and starts arguing with Kahmunrah about who will give what the other wants first, with Kahmunrah comically flipping out whenever Larry reaches out for the hourglass. Unfortunately, Al Capone barges in with an Einstein bobblehead captive, revealing the combination he extorted from it.
Kahmunrah then summons a battalion of Horus Warriors from the Underworld, but the animated giant statue of Abraham Lincoln's memorial (whom Larry befriended earlier) appears, guided by the tiny centurion figure Octavius. Lincoln pummels the Horus Soldiers and frightens them back into the Underworld. Then, Amelia leads every exhibit in battle against Kahmunrah and his armies, who get overwhelmed. Larry tricks Kahmunrah's allies (who plan on betraying him now that he is no longer in position to lead them) into fighting for the leader position.
Enraged by his failure, Kahmunrah attacks Larry with a khopesh (an Egyptian sickle-shaped sword), but Larry holds his own wielding his flashlight and manages to best his foe. Kahmunrah asks Larry "What are you?" to which he answers "I'm the night guard"; before pushing him into the Gates of the Underworld, which Amelia re-opened during the battle, never to be seen again.
Larry later donates a huge sum of money to the American Museum of Natural History to restore it and return the exhibits there, and uses the Tablet's power to have the living exhibits interact with the visitors, under the pretense of holographic animations.