Salathielly
Wait, he drops notes? I haven't gotten to fight him yet due to concentrating on making my ghost grunny, but this sounds intriguing. o_o
Ya didn't know? Thought you saw Crimson and Twizted talked about them in their G-Corp thread at Shadow Lab. >.>;
But yeah, Shadow Jack drops Lab Notes if you defeat him. It's a RIG, but it has journal of what the LabTech studied on Jack's cloak and the kins. There are ten Lab Notes, but so far only four of the notes drop.
You can battle Shadow Jack while leveling up your kins. He appears randomly between Stage 2 to 6 in Gaia Lab Open.
EDIT: Yay! Got my Lapinkin achievement. Now to battle Shadow Jack for the 50x achievement. 8D