You will need to earn 20 additional traits, not counting the core traits or traits temporarily given to you by archetypes. Traits are earned by defeating bosses and aberrations. When each archetype hits level 10, the trait associated with the archetype will unlock permanently and add to this achievement.
Some traits can only be unlocked in multiplayer, so if you’re playing single player, you will need to reach level 10 with 6 archetypes. Make sure you have bonus experience active. Equip the Sagestone Ring (+10%), max out the Scholar trait (+15%, dropped from the final boss) as soon as possible with the Orb of Undoing from Wallace, and keep one of Mudtooth’s Elixir (+15% for 60 minutes) active at all times with 2 traits equipped that are not maxed out.
The Labyrinth
Amplitude
While traversing The Labyrinth, enter a boss room and defeat 4 waves of constructs to unlock the Amplitude trait. Amplitude will increase the size of your Area of Effect (AoE) attacks.
Losomn
Arcane Strike
When you find Harvester’s Reach on Losomn, look for piles of debris surrounded by small enemies. Killing the enemies will unleash a large rat enemy from within. One of the piles may contain an aberration rat instead. Defeating the aberration will grant the Arcane Strike trait which increases Mod power generation from melee attacks.
Recovery
Locate a lonely child while exploring the streets on Losomn (area is random) and escort him/her back to the orphanage. Then, talk with the old woman to receive the Recovery trait which increases stamina regen.
Shadeskin
Clear out all enemies in the boss area with the pyre of the Butcher’s Quarter on Losomn to earn the Shadeskin trait. Shadeskin will increase resistance to elemental status effect damage.
N’Erud
Fitness
Finish off all enemies in the event at the end of Vault of the Formless on N’Erud to unlock the Fitness trait. Fitness will increase your evade distance.
Footwork
Defeat all enemies during the train event in Terminus Station on N’Erud for the Footwork trait. Footwork will increase movement speed while aiming.
Siphoner
Complete the area event by clearing out all bugs as quickly as possible in the Dormant N’Erudian Facility to earn the Siphoner trait. Siphoner will increase lifesteal.
Yaesha
Barkskin
While talking with Meidre on Yaesha (area is random), agree to answer her questions and do so in a way that doesn’t condemn anyone’s life directly (questions are random). Doing so will unlock the Barkskin trait which reduces all incoming damage.
Bloodstream
Also while talking with Meidre on Yaesha (area is random), answer her questions in an aggressive manner to earn the Bloodstream trait. Bloodstream will increase gray health regen.
Blood Bond
Destroy the Root Nexus in Yaesha to earn the Blood Bond trait. The Root Nexus can randomly spawn in different areas depending on the roll of the world. Blood Bond will have you summons absorb damage taken by the caster.
Rugged
Defeat Nexus Root and the Defiler in the boss area of the Forgotten Field on Yaesha. Then, talk to the NPC standing by the Nexus Root to receive the Rugged trait. Rugged will increase the health of archetype summons.
Root Earth
Handling
When you reach the train yard boss area in the Ashen Wastelands on Root Earth, defeat all enemies to unlock the Handling trait. Handling will reduce weapon spread and recoil.
Scholar
Kill the final boss on Root Earth to earn the Scholar trait which will increase experience gained. It’s recommended that you max this out as soon a possible. Talk with Wallace near the docks in Ward 13 and use an Orb of Undoing to reset your trait points.
Wayfarer
Defeat all enemies in the Corrupted Harbor boss area on Root Earth to earn the Wayfarer trait. Wayfarer will increase your movement speed while traversing (climbing ladders, etc.).
Archetype Traits
Archetype traits will only count toward the Proving Grounds achievement or trophy after the archetype reaches max level. At that point, the trait will unlock permanently regardless of which archetypes you currently have equipped. If you are playing in single player and have collected all of the above traits, you will need to max out 6 archetypes. If you play primarily in multiplayer and also have those traits unlocked, you will need to max out 3 archetypes.
Make sure you have bonus experience active. Equip the Sagestone Ring (+10%), max out the Scholar trait (+15%, dropped from the final boss) as soon as possible with the Orb of Undoing from Wallace, and keep one of Mudtooth’s Elixir (+15% for 60 minutes) active at all times with 2 traits equipped that are not maxed out.
After earning all other achievements and trophies, the last of the archetype traits can easily be farmed on Yaesha in The Chimney‘s event. Work your way down to the bottom floor quickly while avoiding the lightning levels below and above you. Crystals may be destroyed to reduce incoming damage. When you reach the center for the first time, shoot the 3 red spheres in the middle to clear a path further down.
Once you reach the bottom floor do not shoot the red spheres in the middle of the room. Doing so will end the event. Instead, focus solely on killing every enemy that spawns. The safest place to do so is in the large alcove near the base of the stairs. When you die, you will respawn at the last checkpoint and can repeat the process to unlock the last of your archetypes. Make sure you swap out archetypes as soon as they max out.
Multiplayer Traits
Glutton
Complete The Feast Event while playing in multiplayer on Losomn in the Great Hall to unlock the Glutton trait which increases the use speed of consumables and relics.
Resonance
If playing in the Dormant N’Erudian Facility in multiplayer, keep one player in the control room to activate the purge to kill the other players. Only those who die will earn the Resonance trait which increases aura size.
Revivalist
While playing multiplayer, revive another player 10 times to unlock Revivalist which increases the speed of reviving and being revived.