Rescue professor Stein. So to say.

Complete any level in single player.

Kill at least 5 headless kamikazes in one explosion.

Secure the bird.

Decipher an Egyptian text.

Complete any level in cooperative with at least 2 players.

Kill an enemy using the Mutilator.

Solve the riddle of the Sphynx.

Kill a Witch-Bride of Achriman.

Smash 20 Kleers with the Sledgehammer.

Power up the Timelock.

Kill 20 enemies with the Minigun without releasing the trigger.

Find Sam's classic outfit

Kill 5 Cave Demons while they're in air.

Gib 20 enemies from close range with a shotgun.

Blow a Major Biomechanoid into pieces.

Use the Mutilator to surf after a Werebull.

Find at least 10 secrets in single player.

Complete the game in single player on unmodified serious difficulty.

Complete the game in single player in the estimated time on each level.

Awake the Guardian of Time.