This achievement requires you to find all six Grandmaster diagrams to each of the Witcher Schools in the game: Feline, Griffin, Ursine, Wolf, and the brand new Manticore School. Luckily you do not need to actually craft all of these pieces of gear; collecting the diagrams and completing their specific Scavenger Hunts will suffice.
To trigger each School’s individual Scavenger Hunts, you must speak to the Grandmaster Smith in Beauclair. His shop, Lazare Lafargue’s Workshop, can be found in the southern district of the city, just south of The Gran Palace fast travel signpost. Speaking with him will unveil details on where each School’s Grandmaster diagrams can be found in Toussaint.
It's worth mentioning that if you actually do desire to craft these Grandmaster gear sets, only Lazare Lafargue will be able to do so at his shop. He is the only merchant in both Toussaint and the entire game with the skill-level necessary to craft such exquisite gear.
Feline SetGriffin SetManticore SetUrsine SetWolven Set