Ascent

You are walking along a railroad track through the wasteland. You are alone. You have no name. Your pockets contain a fortune in money taken from your opponents, as well as their weapons.
You have been walking for some time, and your stamina is draining—you need to kill someone soon.
Behind you: the grave you rose from, a massacre of your doing, and the lifeless body of your only friend. Somewhere before you: the mysterious Pyramid that might hold the secret to your past and abilities.
The Pyramid appears on the horizon, a massive structure containing four levels. You must make your way to the top to have a chance of discovering your identity. You approach the gate, manned by armed guards. What do you do next?