ToME: the Tales of Maj'Eyal

My understanding is that, to start the Lost Knowledge quest, you need to find the item "Gems and their uses" and take it to the jeweler in the Gates of Morning.

1) Is that item something which should appear in every playthrough, or does it have a random chance of appearing or not?

2) Do you need to do something specific to make it possible for that item to appear?

Have you done Eight Legs of Wonder?

No requirements and no guaranty, AFAIK. It is just pure hazard. I have just found the ancient tome in the unremarkable cave, while arriving in the east a couple of hours ago. Sometimes, it is in the armoury or in a pride. And sometimes, I do not find it.

My last run I found it in a High Peak vault, which was quite useless as the character was a yeek.

full luck for everything related to the quest. Also IIRC you can get a yeek out of endgame alive by failing charred scar and sacrificing aeryn (but that would require playing a yeek)