The Chimaeric Demons got their brain crystals when Erik modified the Astral Wolf and merged it with the brain crystal power.
Instead of creating the giant mana wolf, Erik asked the biological supercomputer to make a mana brain crystal.
It wasn't anything physical; it was something that couldn't be found in their brains. It was just a lump of mana that worked exactly like the real deal, but with some differences.
The problem was that to maintain and use all that mana was not as straightforward as for humans. Mana was not a simple substance. It was intangible, impossible to see.
It behaved like a gas, like a liquid, even like a solid. The first time it appeared, people had no idea what it was, and they only learned of their presence after the first brain-crystal-equipped human appeared, and that only by feelings.
It took a while for people to understand, more or less, what they were dealing with.
