|“||I am Kah Mun Rah, the great king of the great kings, and from the darkest depths of ancient history. I have come BACK to life!||„|
Kahmunrah is the main antagonist in Night at the Museum: Battle of the Smithsonian. He is Ahkmenrah's older brother and comes back to life when Ahkmenrah's magical Golden Tablet is brought to the Smithsonian Museum, animating his long dead mummy.
When Larry Daley infiltrates the Smithsonian, he is captured by Kahmunrah, who informs of his plan to use the tablet to open a portal to the underworld and summon a army and take over the world. Larry however manages to trick him, and take back the Tablet. Kahmunhrah sends his soldier to go after him, while managing to capture the animated statue of Custer for helping him but lost the soldiers on the V-J in Times Square with a help from an animated statue of Amelia Earhart. He then recruits the (animated statues of) historical villains Ivan the Terrible, Al Capone and Napoleon Bonaparte to chase him, while ransacking the museum and making it his new palace.
Napoleon & his troops manages to capture Larry & Amelia, due to the noisy cupid statues. The evil pharaoh then takes the Tablet, which he needs to open the Gate of the Underworld to summon an army of Horus-headed warriors, with which he could take over the world. Fortunately, the combination was changed, so Kahmunrah captures Jedediah (Larry's tiny cowboy-figurine friend) and locks him into a filling hourglass, ordering Larry to find the new combination for him before sunrise.
After a meeting with Darth Vader & Oscar the Grouch whom he dismissed, Kahmunrah sees Larry run off with the tablet from a window and thinks he's escaping, so the pharaoh sends his soldiers to retrieve the night guard.
Larry, who got the combination from Einstein bobbleheads, eventually returns and starts arguing with Kahmunrah about who will give the other what he wants first, until Al Capone barges in with an Einstein bobblehead captive, revealing the combination. Kahmunrah then summons a batallion of Horus Warriors from the Underworld, but the animated giant statue of Abraham Lincoln (whom Larry befriended earlier) appears and frightens them back into the Underworld. Then, Amelia leads every exhibit in battle against Kahmunrah and his allies.
Enraged by his failure, Kahmunrah attacks Larry with a khopesh (an Egyptian sickle-shaped sword), but Larry holds his own wielding his nightstick and manges to best his foe, he then pushes Kahmunrah back into his own portal, banished into the Underworld, never to be seen and heard from again. Before he is pushed inside, Kahmunrah asks Larry "What are you?", to which the latter responded "I'm the nightguard."
- Kahmunrah is similar to Loki: Both become jealous of their brother, both are obsessed with power.
- In an original draft of Night at the Museum: Battle of the Smithsonian had Kahmunrah admitting to Larry that he himself personally killed his brother Ahkmenrah for the tablet & for power.