The "Menace From Above" is a large arm that comes through the ceiling to assault you. There are several of these in Mission 05. The very first one is at the start of the storage facility, where you need to damage the 2nd Blood Clot of this mission. Due to the fact that you have to ruin the Blood Clot to advance, it is unmissable. Eliminating the "Menace From Above" is optional. Just assault it with whatever possible. You can concentrate on it with RB to see the health bar. If you take too long or leave, the "Menace From Above" will pull back. If you have problem with this, play on the most affordable difficulty.