Maybe for a extraction of the first hokages cells?
Lol listen. Zetsu is a very mysterious man or whatever he is. Whats been in my head is that zetsu, both black and white have a connection to Hashirama. Wood release isn't just for making trees. Black zetsu's statement, "i am land" made me believe in this very much more. Also, who has Hasi DNA, Orochimaru. He himself conducted several experiments with Hashi's DNA. Zetsu for all we know could have been one of them combined with some sort of plant. Zetsu for all we know, with his recording abilities could have been a spy implanted into the Akatsuki but thats just pure speculation.
And haven't we seen Tobi ooze zetsu like liquid. My guess is Orochimaru and Tobi met once and something went down but we don't have enough info to accurately speculate what could of happened but I bet they both knew of each other. I believed in this further during Tobi's comments about orochimaru in the Danzo fight.
