I don't think the merchant that sells the book has been spawning except in instances and he will not sell it when in an instance.
Once you have and learn the book, Combine 1 X Scraps of Decay random drops from mobs in Demiplane of Decay with 1 Y Template bought from merchants in Demiplane of Decay. So for example 1 Cloth Scraps with 1 Robe Template in Tailoring container makes the Robe HF piece. They are all 450 trivial.
This thread: https://forums.daybreakgames.com/eq...tradeskillers-heart-is-utterly-broken.228231/ discusses it. The book you need is The Lost Art of Working With Wither and Decay and according to that thread and according to EQ Resource: EQ Traders has no further information: http://www.eqtraders.com/items/show_item.php?item=54046&menustr=035000000000 If someone does find out more, I'm sure both EQ Resource and EQ Traders would appreciate knowing.
He's Guktan. Undead. Also, if you look around you'll find some dead merchants in some of the houses, and most of the NPCs inside and outside have something to say to you.
Been camping these for 3 days, nothing. I have even killed all of them several times (after they leave the stalls) no luck. I have killed every mob close to them, no luck. I have hailed and tried to speak to every one of the vendors and every mob in the buildings where they go when off duty, nothing. Just so I am not wasting my time, the Seller of Salvaged Souls is an undead froglok that spawns in place of one of the merchants in the half circle of tents in the middle of the city? Confirmation of this would at least make me feel better about having a bot perma camped there.
I finally saw him after the patch yesterday and bought the book. Now for the drops needed to make the gear...I've seen a total of 1 piece drop while playing every day since TBM was released. . Unfortunately I lost the roll.