To unlock the Master of the Hunt trophy in Assassin's Creed Odyssey, you will need to visit Daphnae at the Temple of Artemis. I unlocked the quest around Episode 3, but I believe it can be unlocked as soon as Episode 2.
Once you speak to Daphnae, she will give you a list of eight legendary animals that you must hunt down. Return the pelts to her and you'll be rewarded with some legendary gear.
Below is a list of the eight legendary animals you will need to kill, their starting level (their level will increase as yours raises) and the closest viewpoint to you can use to fast travel to them.Kalydonian Boar - Level 13
Artemis’s Bow (+20% Damage with Predator Shot ability)
Phokis, Sacred Lands of Apollo, west of Temple of Artemis viewpointThe Hind of Keryneia - Level 16
Drachmae reward, Death Arrow crafting
Eboea, Artemision Point, south of Istiaia Peak viewpointThe Nemean Lion - Level 22
Pandora’s Kopis (+15% damage to animals, buffs to the Tamed Beasts ability)
Argolis, Sinkholes of Herakles, southwest of Sight of Perseus viewpointThe Kretan Bull - Level 33
Master's Artemis Outfit (+15% Hunter damage, +10% bow charging speed)
Messara, Fertile Battlegrounds, southeast of Temple of Artemis Diktynna viewpoint (Little Egypt)The Lykaon Wolf - Level 36
Master's Artemis Treads (+15% Hunter damage, +10% bow damage when using Charged Shot)
Lakonia, Dioskouri Peninsula, south of Helot Lookout viewpoint (Helot Hills)Kallisto the Bear- Level 37
Master's Artemis Belt (+13% Hunter damage, +12% damage with bows on distant targets.
Arkadia, Golden Fields, west of Temple of Poseidon viewpoint (Argos)Erymanthian Boar - Level 38
Master's Artemis Gloves (+15% Hunter damage, +25% adrenaline upon headshot kill)
Elis, Erymanthos Foothills, southeast of Ionian Watch viewpoint (Istion Valley)The Krokottas Hyena - Level 39
Master's Artemis Hood (+13% Hunter damage, +20% headshot damage)
Kythera, Skandeia Bay, north of Sacrificial Altar viewpoint
Once you have returned with each of the eight pelts, Daphnae will change location and move to Chios. Visit her for a final quest which will give you a choice to make. Which choice you make doesn't matter, so I'll avoid revealing spoilers.
When the final quest has been completed you'll unlock the Master of the Hunt trophy.
If you haven't unlocked the I am Legend trophy by this point, you can equip the legendary armour you receive throughout this questline to unlock that trophy as well.