Where can i find Stack effect 20/30 for DB

and Chains of hell 20/30

Don't DB's initial skillbooks(that ones that'd give other classes a level 10 mastery) give an automatic level 30 mastery from the get-go?

final cut and chain of hell skillbook drop from zak, when you use it, it go to mastery lvl 30 already, no need of any other book to rise its mastery lvl.

The mirrored target 30 skillbook drops from chief oblivion guardians, so it should be fairly easy to find.