Mjollnir's Power can be obtained around twice per world, usually once per level and once per temple; and is often hidden in walls, or beneath the floor. Early on in the game, these areas may be easily noticeable due to visual hints such as cracks in the walls/floors, however their location becomes increasingly hidden with each level.
World One - JungleEdit
Mjollnir's can be found for the first time in the Jungle Level, shortly after encountering the Kneebiter for the first time. After leaping over two spike pits, the player will encounter a rope. By ascending it they will progress further into the level, but if they climb down to the very bottom of the rope and take two swings at the wall to their right, it will break to reveal Mjollnir.
Mjollnir can be found for the second and final time near the beginning of the Jungle Temple, shortly after the 'spear platforming puzzle' and the series of five Arrow Dispensers. After killing the second Nuptup, break the floor underneath where it was to reveal Mjollnir once again.
World Two - WaterEdit
After Encountering the first homing mine and jumping onto the very small platform shortly after, throw a spear at the wall to the left, revealing Mjollnir.
Approximately half-way through the Water Temple, after dispatching a group of Myrmor consisting of a Defender, Charger and a Leaper seated upon a heightened platform. Using a spear to ascend the wall to your left, above the drop into water guarded by two Slymes. From as high as possible, leap onto the now-deceased Leaper's platform, and attack the gold wall to your right. This should reveal Mjollnir.
After sliding down a ramp and jumping onto a series of three ascending narrow platforms, drop down while destroying the mine, and strike the base of the third platform, where Mjollnir resides.
Water Temple (Valkyrie)Edit
After dealing with two Defender Myrmors at the bottom of a descending ramp, jump and throw spears at the wall above some water, then jump to reach Mjollnir.
World Three - UndeadEdit
As you drop down through the first dissolving platform immediately after meeting the first Seargent Crunch double jump to the left wall. Mjollnir is in the wall on the narrow ledge.
sliding down a ramp that is far to the right of the checkpoint, you will encounter a Skele-Ton. After defeating it, attack the wall directly behind it to reveal Mjollner.
After defeating your first Seargent Crunch, you descend into pits full of zombies. Going to the right will make you progress through the level, while going to the left reveals a chest on a platform at the end. Under this platform, hitting the wall at the extreme left reveals Mjollner.
Undead Temple (Valkyrie)Edit
Right after falling from the very first dissolving platform, and sliding down a slope, you fall right behind a Mc Stabby facing right. If you hit the wall on your left, you will find Mjollner.
World Four - Snake CultEdit
Right above where you see the first bat in the level there are two pillars that are not in line with eachother just to it's left. The Mjollner is on the top of the bottom pillar
there will be a point about midway in the level where there is a bat hovering over a fire pit to the right of the player. Attack the wall on the other side of the bat to reveal Mjollner.
At a third of the level, right after defeating two Cultist in a row, there is a small level change. On top of it stands a chest, with three Batchoos above it. Right before this level change, you can see stones below the ground: you can actually break the ground at this location, falling into an underground tunnel, where you'll find Mjollner.
Snake Cult Temple (Valkyrie)Edit
At the very beginning of the level, right after passing the two Cult Leaders facing each other, you'll be faced with another Cult Leader at the end of the rope. If you look carefully, the ground texture continues inside the wall behind it. After killing it, hitting the wall will reveal Mjollner
World Five - AirEdit
On the ship where you climb to another ship from it's dangling chain; you can instead fall off the edge onto a golden colored ledge and attack the engine; where a captain's cabin would be on a pirate ship
At the bottom of the vertical air tunnel with the multiple Toadys hit the wall directly to your left and you will see Mjollner.
Just when you spawn, at the poop of the flying ship, if you walk (carefully !) to your right, past the Valkyrie, you should land on a small yellow platform. Hitting the wall at this location will give you Mjollner, and open a path to the yellow stair on the side of the ship, which will let you get back to the deck and pursue the level.
Air Temple (Valkyrie)Edit
Near the end, you fall into a pit with a light air lift, and three Toadys jumping on you from the side. When you reach the bottom, you can jump right and continue the level, but if you hit the wall on the left (directly facing the right exit), you will find Mjollner.
Far into the tower you will find Mjollnir's Power near the entrance. There will be a shallow pit before you with 3 Spitters on the opposite side on a platform. Fall into the pit and attack the wall to your left to reveal it.
Fafnir's Tower 2Edit
Hitting the first Pyrefly will make Mjollner appear in the hole in the wall, at the right of the first rope. The bounce from the Pyrefly should let you grab the rope again, and go get it, or you can just fall and work your way up with spears.