No real secret to these. There’s a whole mix of various kits. Most are Oathmark Goblin torsos, with some Fireforge, Gripping Beast, Frostgrave and Gw torsos. Heads are a mix of Oathmark, Warlord, Frostgrave, and some others I can’t remember, arms are Oathmark, Perry, Fireforge, with some Fireforge polearms added in. Lots of green stuff fur and hoods to cover up awkward joints and cut marks.
So I had a vision of what I wanted, I blu-tacked a few bits together until I liked what I saw and then got completely carried away making them. The variations are endless and it’s actually great fun. I didn’t buy whole boxes of kits other than Oathmark, but lots of single sprues on eBay.