A total of 15 Nix Treasure collectibles can be found in Star Wars Outlaws. They are located on four planets: Toshara, Kijimi, Tatooine and Akiva.
Nix treasures locations appear on the map as you approach their locations. When you find one follow Nix and he will eventually lead you to a mound of dirt he will dig up for you - collect the treasure hidden inside.
Once you find and collect them all, you will unlock the "Got you something" achievement / trophy.
Amberine TunnelRelated treasure: Gun Piece.
Carver's MazeRelated treasure: Shiny Lump.
Droid Eye
Gun Piece
Gushiro CanyonRelated treasure: Secret Amulet.
Liar's RestRelated treasure: Lucky Cubes.
Lucky Cubes
A pair of Sabacc dice from some old casino.
Nix seems to like chewing on them.
Secret Amulet
Shiny Lump
Tree NestRelated treasure: Droid Eye.
Twinkly Metal
A wind chime pearl from a Tosharan flying trap.
It makes a calming noise when Nix makes it roll.
Windy CliffRelated treasure: Twinkly Metal.
Picture Card
Secluded Backalley
Back Alley
Bang Button
Dark Cave
Hammer Rock
Horns
Mine Cart
Strange Pillar
Tiny Ship
Fruit Wrapper
Haunted Lair
Kowakian Den
Old Money
Smelly Bone
Sodora Falls
Talk Box
Temple Ruins