Rex's plan works majestically, it was very effective to draw the truth from these Black Hands.
In the end, he got the information that he needs. Based on what the three Black Hands confessed, this started suddenly when King John picked a couple of Black Hands to be bestowed with the power.
None of them know where King John gain this power, but they were excited.
Promised that they would gain insurmountable physical strength, capable of propelling them into a higher realm, the chosen Black Hands gratefully accepted this generous gift. Moreover, they feel special as only a few were chosen from the thousands of Black Hands.
But a few days after that, there was an issue to attack the Supernatural territory.
No particular reason was provided, yet nobody complained.
