What Minos had planned was to use the greed of some individuals with positions of power in that family to deceive them, making them keep information about the Dry City.
Minos no longer had many options for action. So, he considered using a portion of the truth about the Dry City to demonstrate to the Gill family elders how valuable this place was. And how bad it would be if they just delivered it on a 'platter' to the local royal family.
That is, it wouldn't take a genius to figure out that the Brown family would surely take over the Dry City if they found this place valuable for them. Moreover, if some noble family denounced Minos and his forces about any infraction that had happened, they would use that as an excuse to occupy the Black Plain!
