Merlock is written "マーロック"(Marokku)in japanese. His main ability is to shape-shift/transform(お化けobake), into several creatures, such as nonhuman animals(i.e. Birds, big cats, bear, etc)and mythological creatures(gryphon, dragon).
I find it funny that he keeps his mustache no matter what creature he can transform.
I think that he would be the only one that can use the amulet/talisman and if he wants to turn into a new creature he would need to train it till that transformation is perfect and be able to use that new shape. And each creature requires a different amount of time and training.
Correct me if I'm wrong on something or if my english is weird!:)