"Use 2 Berserk Darts on guards" is an optional mission objective in Sequence 4 / Memory 4: Overrun and Outnumbered
Walkthrough[edit]
Berserk Darts draw a lot more attention. After a brief pause, the target will enter an uncontrollable rage and attack anything they can see: friend or foe. This is a great way to clear out foes. Use these carefully and only when there are only a few hostages none.