Since Khaos was the last lycan, it meant he would never find his destined mate, thus his attachment to the Shell was the closest thing to it.
And that was the fact that made Rhett worried the moment Khaos started to show his overprotective side toward Zuri. The lycan was known to be very protective to their mate, to their family. They would never step out of the bond that they created with their other half.
And from the look of it, Khaos unconsciously had created that bond with Zuri. The attachment that they felt for each other helped in that case.
Therefore, when Elijah told Rhett about how Khaos was reluctant for inflicting the curse on Zuri, he knew what would happen if he didn't intervene.
If they couldn't talk to Khaos, then the only option was letting Zuri to want it. Rhett knew his sister…