Defeat the infected Hand of Aegaeon

Story related. Cannot be missed.
Will unlock in Chapter 4: The Guard House.

Megaera will infect a Hand of Aegaeon with her insects and will attack you, starting the first mini-boss battle that you encounter. In the first stage you will be fighting it horizontally. Dodge its attacks until you are prompted to grapple it. It will then destroy the bridge, writhe around and you will be fighting it vertically, with two pits on either side of you.

Use the pits to dodge its drag attacks, where it plunges its claws into either side of the bridge and pulls them across. Repeat this until you see the red grapple prompt appear. Successfully perform the QTE and the trophy will unlock.