From MM6 Wiki
The staff is the traditional weapon of the oppressed. This one is unremarkable, and the ruby at the end of it is actually just colored glass.
Magically light and hard, this staff is made of a rare wood stripped from the Elves during the Timber War in 600 A.S. The emerald at the end of it is real, and probably serves as a magical reservoir from which the staff draws its strength.
This staff, along with others of its kind, was found in the treasure room of the Necromancer's guild after their disastrous defeat by Roland at the end of the Succession War.
Traditionally carried by the High Druid, but lost during struggles over religious doctrine, Merlin acts as a reservoir of spell power the wielder can draw upon at any time. Merlin is enchanted with swiftness, and rains blows upon enemies much faster than an ordinary staff.