Theories

The Wandering Shard / Broken Mother / Shattered Guardian (?) is orbiting the portal to the Far Realm in The Astral Sea (Riga can see both at night, still waiting for confirmation that after that crit she knows what the black hole is). Said Far Realm might also be "The Beyond". So there's a strong chance that a lot of the differing properties of Malachite might have to do with the influence of the Far Realm (like for the Shards)
I read Ravik's convo with Sardior, and he mentions a "key" being lost in the same breath as Tural's shard within Daenur. Walleh's "secret" that Riga could read also mentions a "first key", which is not Daenur, and associates it strongly with a feeling of Freedom.

Deepest One and Gnolls

The ritual to summon Gnolls is extremely unoptimized, by design. Something is leeching the excess magical energy. It might be the Deepest One doing the leaching. Someone's piggy-backing on Yeenoghu's endless syphoning.
Telepathing to the book might provide a link to the Deepest One. Or one of the Shadows Elders.
This is either a recruitment booklet or a radicalizing one. In the former case, it's likely to see use not on Gnolls, but other like-minded individuals.
The book puts a certain emphasis on the concept of Yeenoghu eating "memories". It is possible that the Deepest Shadows are "converting" the Tabaxi Enshrouded into Gnolls, preserving their skills while wiping away their experiences (and seeds of dissent / rebellion, like Trick).
From Xarla's Book and the missing child in Mardon: There's a chance Xarla was a child before being turned into a Gnoll Channeler.

#trine 23-04-25: maybe the people of Mardon was turned into gnolls, somehow.
#alex 4/23/25: This hasn't come up IC yet, but people's bones were found in Mardon. Unclear if enough to account for all inhabitants, but definitely enough for several.
- Then again, if we flip events around:
- Gnolls / hyenas consume Mardon's supplies
- Some people are forced to feed/force fed Gnoll meat, with a Channeler present, and then sicked on the others.