The file wasn't completely helpful, and he hasn't tried his nen or his other powers really. Not yet. When he's alone he will. For now- his file barely mentioned anything about nen, or anything similar, so he's left to assume till he gets the time to try it.

"Blank slate?" He'll get from that what Chrollo means. Blank slate means potential. What you'd tell a criminal that has been wiped clean of his crimes, able to do as he pleases once again. So Chrollo means he's been given a new chance?

"And what will you fill it with then? I'll have to save my own tricks for myself, but you can 'have' them one day." Have as in, all over your body right, when he beats the shit out of you. Mmm- if he's strong enough to- unless Chrollo's strong enough then to stop him.

If not, it'll be his life running through his fingers. Make him squirm for him- this magnificent man. Ahh~