It was never stated by anyone what it was. To avoid drama most likely. It tied in to Sopphora's expansion, which is itself tied neetly to Zheng Shi. So neither that or the Jumper bunnies, or Roo will receive any content updates soon.
I searched up William's response regarding that matter for you, if you wanna read it.
Crazy really that his content is already on ice since for over a year now by the way. I myself would get some serious writer depression if I was forced to not work on my own stuff for so long, if I was in his shoes, and would be forced to just be the Phaedra 2 writing slave instead.