1 - After defeat Mulvik, leave cave, there you can unlock new village

2- Then you leave the village (go right) and see rives and there you can see firefly

3- After using warp rod and see cave nearby firefly, enter in cave
You see this

4- (Firefly moves slightly strange) and this is a main thing
For obtain reward just push ground plate ( right, down, up, left, right, left)


5 - and then you obtain a key fragment