Set (Original Timeline)

Set (sometimes Seth) was the Egyptian god of evil, war and destruction. He is often represented having a jackal face. After Lara took the amulet off the sarcophagus that he was imprisoned in, he and his power was awakened leaving it up to Lara to stop Set since she was the one that had the amulet that could keep him imprisoned forever but she had a time limit. She must imprison him before the solar eclipse or the whole world would have been doomed and everything would be destroyed.

Tomb Raider The Last Revelation
Set sayeth Possessing Werner Von Croy After preventing Horus' arrival
 * "I am the shadow across the sun. I am the bringer of plagues. My wrath will consume all lands and shall be ceaseless."
 * "We have it, the ancient Ceremonial tablet. Take it and prepare it, and see if the Croft woman has arrived with our armour."
 * "Come in, Lara. I have been expecting you. Come to me, child. Do not fear your old colleague. I merely require the armour that you hold in your possession."
 * "I will grant you vigor as those around you fall, you shall command the ultimate power: that of life or death over those you choose at your side and in return they will bow at your feet and give worship."
 * "My wicked cousin is once again returned to the stars. It is I who shall rule over this world once more. Come forth and kneel and bow before your god before he extinguishes your worthless life."

Trivia

 * In the Prima guide for Tomb Raider IV, Set is mistakenly called Horus in the final level. Many guides make this mistake.
 * Despite being linked with jackals, Set isn't really a jackal headed god. Anubis is. In Ancient Egypt, Set has the head of an unknown animal. Perhaps it was thought that it wouldn't make much sense to have Anubis as the main villain since he isn't really a 'evil' god and isn't an enemy of Horus. On the contrary, Anubis helped create the first mummy, Horus' father Osiris, who was murdered by his brother, Set.
 * Core Design went with spelling his name as Seth. Which means it is pronounced as 'Set'. Both 'Seth' and 'Set' are names of the Egyptian god anyway, both pronouced the same way.