Strange Brigade

This is story related and cannot be missed.

At the end of the level, you will enter the ancient temple. There you will be introduced to Bes, Defender of Egypt. He proceeds to tell you now that Ammit the Devourer is slain, nothing guards the gates between the Realm of the Living and Realm of the Dead. He then instructs you that his shield must be reforged to put an end to this madness.

After stepping on three blue circles and shooting three blue orbs, the spikes guarding the shield will lower. Run up to the shield and hold to collect its souls. Bes will then say that the First Damned have already risen so you need to stand your ground and defeat them. When you’ve reached a certain point, the Island's Grand Champion appears. To defeat it, you need to damage it by shooting the glowing blue orb on its chest, then its back then its head. When it is defeated, all of the remaining enemies disappear and you are free to collect the shield piece, unlocking the achievement.