In fact, the Stealing Abilities divine ability can steal and use more than one divine ability at the same time. So not only can one rank 4 divine ability turn into a rank 9 divine ability, it can turn into many rank 9 divine abilities too.
The number of divine abilities that can be stolen and used at once is dependent on the mastery of divine ability. Thieves gain one slot at 1%, 10%, 20%, 50%, and 100% mastery. So they can use a maximum of 5 stolen divine abilities with their single rank 4 divine ability.
Since Thieving Hammer just became a rank 4 godclad, the mastery of his divine ability is at 1%. So he can only use one divine ability currently.
He used this one slot for his rank 4 divine ability to steal the rank 1 divine ability of a rank 1 assassin. The rank 1 assassin became unable to use Cloak, while Thieving Hammer became able to use Cloak as well as any assassin.
