For this achievement you must destroy all the sarcophagi in the level. to do this you must have the large enemies throw a fire ball at you which will hit the ground and you'll pick it up, once you reach one of the sarcophagus in the level and press the
to spit the fireball at them destroying them. You'll notice what they look like right away when you enter the level. they'll constantly spawn enemies if they are not destroyed. After destroying the last one the achievement will pop. I will also point out that I got this in main level and not the Agent 9 mission for his mission does have you destroy sarcophagi as well as a bunch of enemies so the Agent 9 mission doesn't count as far as I'm aware.