In the bloom you can buy a slave named Coty.
Buy him and then tell him you will set him free. Then offer to find him work.
Ask Brusca who is guarding the gate to the Memovira's fortress if she would take him as a soldier. Convince her to take him and tell Coty.
Later, near the grand finale of the game you will fight the Memovira and her allies, the bloom and the Sorrow. Coty will take your side and attack your enemies and the trophy will pop.