This page lists the locations of all 8 Master's Emblems. The reward is the Magic Bell, which makes magic cost 0 GEMs.
The Master's Emblem A ☉
The Master's Emblem A ☉ can be obtained after you get the Zantetsu Sword in Dr. Leo's Laboratory. Go back to Grass Valley and enter the World of Evil painting. Use the Zantetsu Sword to kill the spinning Metagrinners that you couldn't hurt before. There are three lairs in the painting that you can clear. After clearing those lairs, go to the southeast corner of Grass Valley, go west past the small cabin, and go up the ivy. Walk to the far west side of the ledge to find the Master's Emblem A. The emblem has a symbol of the Sun on it.
The Master's Emblem B ☿
The Master's Emblem B ☿ is in Magridd Castle, in the basement. Go to the area of the basement that has spikes on the floor. Go to the northwest corner of the area where there is a diagonal line of spikes. There is a hidden chest northwest of the spikes that contains the Master's Emblem B. If you have trouble finding it, clear all of the lairs in the torture room and basement and get the VIP Card to enter the Left Tower (check the Magridd Castle section if you need help). Clear the lairs on the first floor to release a soldier who knows all about Magridd Castle. Go talk to him and he joins you as the Soul of Reality. Go back to the room with the diagonal line of spikes, then the Soul of Reality will reveal the hidden chest that contains the emblem. The emblem has the symbol of Mercury on it.
The Master's Emblem C ♀
The Master's Emblem C ♀ can be found in GreenWood. Go into the tree house on the right that has two squirrels. Talk to the squirrel on the right to get the emblem. The emblem has the symbol of Venus on it.
The Master's Emblem D ♂
The Master's Emblem D ♂ can be obtained in St. Elle's Seabed. When you release a dolphin on the west side of the Seabed Sanctuary, talk to it and stand in front of its nose. It will push you up to a treasure chest. Open it to get the Big Pearl. Walk in front of the dolphin's nose again to go back down. Then go into Lue's prison and use the Dream Rod on the sleeping dolphin on the left. Equip the Big Pearl and talk to the dolphin to make it swim away from the unlocked lair. Open the lair to create a path. After the dream, equip the bubble armor and go underwater. Go northwest to the cave entrance there. You will be back in the area that you saw in the dream. Check the west wall to find the path that you opened in the dream. Go into the cave at the end of that path. The northwest chest contains the emblem. The emblem has the symbol of Mars on it.
The Master's Emblem E ♃
The Master's Emblem E ♃ can be obtained in the Mountain of Souls. Find the sleeping mushroom in the jail and use the Dream Rod on it, and clear the lair to create a path. Then go to that place in Lune. There is a lair there that you couldn't reach before. Clear it to release a snail. Go back to the Mountain of Souls. Go south from the warp tile and walk into the wall just left of the middle lamp. You will go through a secret path to the snail that you released. Talk to it to get the emblem. The emblem has the symbol of Jupiter on it.
The Master's Emblem F ♄
The Master's Emblem F ♄ is in Lune. Find the sleeping mushroom in the jail and use the Dream Rod on it, and clear the lair to create a path. Then go to that place in Lune and walk to the top edge of the island to find the emblem. The emblem has the symbol of Saturn on it.
The Master's Emblem G ♆
The Master's Emblem G ♆ is in Dr. Leo's Laboratory. When you release the chest of drawers in the southwest room, go into that room and push the chest of drawers to the left. Walk onto the spot that the drawers were covering to find the emblem. The emblem has the symbol of Neptune on it.
The Master's Emblem H ♅
The Master's Emblem H ♅ is in front of Magridd castle. Go up the eastern bridge toward the castle, but don't go in. Instead, walk behind the three pillars to the left, and go as far left as you can go to find the emblem. The emblem has the symbol of Uranus on it.
The Magic Bell
After you obtain all eight Master's Emblems, you can get the Magic Bell, which you can equip to cast magic without spending GEMs. To get it, go to GreenWood and talk to the deer in the southwest corner of town, past the crocodile. The deer will walk north to a tree. Talk to it and it will headbutt the tree until a blue crystal falls down. Talk to the Blue Crystal Fairy and she will exchange your eight Master's Emblems for the Magic Bell. Equip it to cast magic without spending GEMs.