I finally pieced together what Damain has been doing in the sewers. We first see him in the sewers in Batman & Robin #9 searching for something in the sewers. At first, I thought he was looking for clues of his father’s whereabouts during the Court of Owls arc. I thought that was kind of sweet. But that hypothesis was proven incorrect when we see him in the sewers again in issue #13.
Then I saw issue #14 and I was so freaking confused where the hell he got that pearl from. Until I finally figured it out! I don’t know if anyone else figured it out before me, but it totally broke my heart when I realized it.
All that time searching and making a rat friend, he was looking for his grandmother’s lost pearls.