Michael did not just intend to deepen the cooperation between Lustra and the Henshaw Family, but another aim of his was to compensate them for their loss when he took Ignis. While he had forfeited a lot in order to claim Ignis, he knew that what he had gained was many times more than what any other party had gained from that expedition. That was why Bellar was so irritated and agitated at that time. If not for their display of power, Craig's support, and the Henshaw Family's support, then it would certainly not have been an easy feat to take Ignis.
"A mana crystal mine..." Jacob whispered from the side and Michael mentally nodded.
The stash of fire attributed mana crystals had been a result of the presence of a powerful fire attributed being having made that area their home for a long time. That was what had happened with Ignis. Now that he had left there, the cavern and tunnels would no longer produce mana crystals, whether pure or with attributes.