Lara Croft, famed explorer, thought she would be first to arrive at the temple, but up-and-coming archaeologist Carter Bell beat her to the entrance. They each hoped to find the mythical Staff of Osiris, but they discovered more than they bargained for.
The Temple was a prison for Horus and Isis, the last of the old gods not bound to Set. Seeing the Staff, Carter removed it from a mechanism, setting off the trap meant to keep Horus and Isis imprisoned. Lara and Carter now find themselves marked for death. Horus and Isis, freed from thousands of years in prison and in possession of the staff, promise Carter and Lara they will help them resurrect Osiris, the only god capable of saving Lara and Carter from judgement, and the only power that can hope to defeat Set. With a common goal of finding the fragments of Osiris, and stopping the return of Set, the companions form an alliance.
As they fight their way across the sands, they must face gods and monsters of myth and legend driven mad and controlled by Set. At stake is the fate of the world, as Set marshals his powers in order to return and reclaim his throne in the world of the living, with an army of the dead behind him. Set knows the prophecy has come, intent on remaking the world in his own image, a nightmare of storms and death.
In the comic style introductory video we see Carter Bell beating Lara to the Staff of Osiris that has been hidden in the pyramid for thousands of years. As he grabs it, he inadvertently frees the evil god Set, who had been imprisoned in Duat, the ancient Egyptian netherworld. Lara and Carter get the Mark of Ammit
impressed on their hands; they are now marked for death by Ammit, the soul eater, who devours the soul of the sinners.
But together with Set Horus and Isis are reawakened who had been tasked with keeping Set locked up. Together all four enter the tomb in order to stop Set and his minions from taking over the world and bringing eternal darkness, all while being hunted by Ammit.
As the player takes over the characters, they have to wander deeper into the tomb. As this is a training tomb, they first learn how to use their gear. Lara or Carter, aka the mortals or the adventurers, have to fire up the Torch and set light to two Braziers to raise two blocks from the ground. Then Isis/Horus, aka the two ancient gods or the Egyptians, need to use the Staff of Osiris to close a Set's Mark in order to open the next door. After that the player learns about pressure plates and has to shoot a giant Rotating Eye.
Meanwhile Set raises the first of his undead Skeletons that attack Lara and her companions. Another column, covered in ancient blue glowing glyphs, called Glyph of Osiris, can be raised with the help of the Staff of Osiris. Now the mortals learn how to use their grapple to climb steep walls and getting other players across, while the Egyptians can use their Shield to get other players to higher ground. But all of them can use Bombs to destroy the following Arrow Traps.
Soon after the travellers can collect the first ring. Unlike all the other Rings and Amulets in the game, which are hidden inside Treasure Chests, this one lies on the ground and can simply be picked up. This way the player can start to modify his or her skills.
Crumbling bridges and a Sun Ball puzzle follow. Soon after the players find the Iron Fire Flail amulet. Finally the voyagers have to escape a chasing Ammit across crumbling arches littered with traps.