During your fight with Raven, you need to bring her down non-lethally. If you are using the tranq pistol, aim for the head - that maximizes the damage to her psych gauge.
Do yourself a favor and stay on the stairs as well - you can avoid a lot of her missile attacks laying prone.
Once you have depleted her psych gauge, she will lose her wings and really, REALLY want to give you some hugs. At this point, run up the stairs to the very top of the tower. In one corner of the structure you will see the "Raging Raven Doll". Snag it, and this trophy is yours.
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