⚔️ The Griffin armor diagrams are in Velen.⚔️ It has a level 11 requirement.⚔️ You'll have to fight wraiths, endrega, an ekimmara, and a wyvern to get them.⚔️ The upgrade diagram locations come from buying Edwin Greloff's maps at the Midcopse blacksmith, the Hierarch Square armorer, and Éibhear Hattori, once you complete Of Swords and Dumplings.
The Griffin armor is a medium witcher gear set mainly focused around buffing the power of your signs, but also turning your Yrden into an AoE that reduces the damage you take, and further increases sign intensity when you're in it. There are four armor pieces, two swords, but no crossbow.
The diagrams to forge the basic Griffin witcher armor are located in Dragonslayer's Grotto in east Velen, to the northwest of Downwarren. The video above shows the route through this ruin, but otherwise:
Head inside, fight the wraiths, take a left at the end of the corridor and use Aard to blow open the cracked wall on its left side.
The next section is filled with poisonous, flammable gas and wraiths. I suggest just ignoring them and running straight through to the far end, where you'll find a rock barrier you can blast open with Aard, and a room with an ekimmara to slay on the other side.
After killing the vampire, grab the armor diagrams from the chest up the stairs on the platform above.
Read Witcher George's Journal, also in the chest, to get the location of the Griffin Silver Sword and the Griffin Steel Sword, both of which are also in the Velen region. Remember, there is no crossbow in this set.
Griffin Steel Sword
In Hindhold watchtower in north Velen, directly east of the Border Post. Be prepared to fight endrega workers and warriors.
Griffin Silver Sword
In Lornruk lighthouse in west Velen, north of Heatherton. There's a wyvern nesting and you'll have to enter underwater via a cave with drowners.
Once you've crafted the basic armor, you can upgrade it to enhanced, superior, and mastercrafted by finding the relevant diagrams.
Enhanced: Buy Edwin Greloff's first and second map from Midcopse's armorer in west Velen, southwest of Crow's Perch.
Superior: Buy Edwin Greloff's third map from Hierarch Square's armorer in the center of Novigrad.
Mastercrafted: Buy Edwin Greloff's fourth map from Éibhear Hattori once you complete Of Swords and Dumplings. His home is northwest of Novigrad's Glory Gate.
🐈⬛ Feline: A light set for glass cannons🐻 Ursine: A heavy set for high defence🐺 Wolven: A medium all-rounder set
For grandmaster, when you head to Toussaint in the Blood and Wine DLC, speak to Lazare Lafargue in his armor shop in south Beauclair to start the 'Master Master Master Master!' quest to find the diagrams.