To unlock the Predator and Prey trophy in Assassin's Creed Odyssey, you must purchase Episode 1 of the Legacy of the First Blade content or own the season pass, and download the episode.
You must also have completed the Shadow of a Legend quest, the second quest in the Episode's quest line.
There are seven members of the Order of the Hunters to track down, but luckily three of them will be targets during the main quest anyway, leaving four more to find.
Story spoilers dead ahead!
1. Timosa the Physician - revealed and killed during the main quest
2. Phratagoune the Keeper - revealed by a clue from Timosa. She's up near a bear den in northern Makedonia. Careful -- she's a handful and has a massive bear pal. Gather all bear pelts from the den -- we'll need five of them later.
3. Konon the Fighter -- Phratagoune will give you the clue. He'll appear in a camp called Xerxes’s Sacrifice of the Nine in northern Makedonia.
4. Echion the Watcher -- During the Dead Man Rises quest chain you will be asked to bring someone five bear pelts. Do so and answer "...and we are the Order" when prompted to get Echion's location. You'll find him out in the open in the Roots of an Empire sub-region.
5. Bubares the Conspirator -- revealed and killed during the main quest
6. Akantha the Deceiver -- when grabbing the document during the Revealing the Recruiter main quest, make sure to pick up the other documents in the same room. One will reveal Akantha in the Leader House in Asklepion.
7. Pactyas the Huntsman -- Complete the main quest.
Once you have defeated all Order members you will get the trophy. Remember that you have to confirm each kill.