Hey there,
Crystal keys are a good source for a random chance at any clue scroll as a start..
Easy Clues - Low level mobs drop them fairly often or can resort to catching and looting Gourmet implings for them (I think 1/25 chance?).
Medium Clues - Barrage/Chin Dagganoths in catacomb for a good chance for them or kill battlemages in mage arena as they drop them fairly often, else resort to catching and looting Eclectic implings (found in Puro Puro + there's a plugin to highlight these implings for you).
Hard Clues - From high level slayer + hellhounds have a good chance to drop them or catch and loot Dragon implings.
Elite Clues - Commonly found by doing bosses such as Olm and ToB.
Master Clues - Random chance to get them from opening a clue chest from the aforementioned difficulties or a also crystal keys/enhanced crystal keys would drop them but kinda rare.
Alternative Method: Catching and looting Lucky Implings from Puro-Puro for a random clue reward (random rate from all clue difficulties).
Goodluck!
~Ipoy
