Albert Einstein's liquid

This unnamed liquid was in the possession of Albert Einstein, who thought it to be bionic fusion liquid for his time machine. After Einstein and his liquid were accidentally transported aboard the Doctor's TARDIS the Eleventh Doctor informed him he was wrong about the liquid, but before Einstein could conduct more tests on it the liquid bubbled from its flask, splashed onto Einstein, and transformed him into an Ood. (DW: Death is the Only Answer)