All of The Boomsday Project Puzzles Cleared - Earn Your Card Back Easy! - News - HearthPwn
Dr. Boom Puzzle Lab Solutions Guide - Dr. Boom Puzzles List, Answers, & Tips - Hearthstone Top Decks
Puzzle Lab - Hearthstone Wiki
Puzzle Lab Guide - Release Date, Answers & Solutions, Card Back - Hearthstone Top Decks
The tasks in Mercenaries actually start giving quite big rewards later on, definitely worth farming from Mysterious Strangers beyound the item at 7! : r/hearthstone