Kahmunrah is the older brother of Ahkmenrah. He wishes to get his brother's magical tablet so that he can open the door to Duat (the Egyptian underworld).
Night at the Museum: Battle of the Smithsonian
He rules the Earth and the Smithsonian museum with an iron fist, and then joins forces with other historical leaders such as Napoleon Bonaparte, Ivan the Terrible, and Al Capone. Later, modern screen villains, which include Oscar the Grouch (from Sesame Street) and Darth Vader (from the Star Wars films), also want to be on Kahmunrah's team, but the Egyptian king does not let them (Oscar the Grouch is not evil at all and Darth Vader does not speak but tries to use the Force, which naturally does not work and Kahmunrah does not understand the hand motion).
Kahmunrah discovers the combination on the tablet has been changed, and coerces Larry Daley into finding out the new combination by trapping his cowboy friend Jedediah in an hourglass. He later learns the combination after Al Caponeinterrogates a bobble-headed Albert Einstein (it's pi), and uses it to open to the gate to Duat, unleashing an army of falcon-headed warriors. These are sent back to the underworld by the Abraham Lincoln Statue. Kahmunrah is later banished to Duat by Larry Daley and he is never seen or heard from again.
- In an early version of the script for Battle of the Smithsonian, a conversation between Kahmunrah and Larry reveals that he murdered his younger brother Ahkmenrah. This conversation was scrapped.
- One interesting thing to note is that while the coffins of Ahkmenrah and his parents were found on the Nile Expedition, the coffin of Kahmunrah wasn't present. This would serve to confirm the strained relationship that Kahmunrah had with his parents, as evidenced in the second movie that his parents "may have slightly changed the combination on [him]," since he wasn't buried in the same tomb as the rest of his family. Perhaps, he was never buried at all, and his body was lost in the desert the whole time, which would explain why Ahkmenrah becomes a mummy when the Tablet's power wanes, whereas Kahmunrah becomes a mannequin; Kahmunrah's spirit is still present, but the body which houses his spirit in the 21st Century isn't his own.