Burial Grounds
The Burial Grounds is a land that's unlocked once the player has unlocked the Orb of the Sword in the Kraken Depths. It consists of large patches of empty land with the occasional burial mounds (barrows).
Barrows consist of solid walls that encase treasure inside; these walls cannot be destroyed by the player's weapon, but must be destroyed with the Orb of the Sword. Initially, only one of the two types of walls can be cut by the sword; so the player must learn how to rotate it relative to the map, even though the sword does not change its orientation when the player moves around. This can be done by exploiting the fact that the angles of a triangle in hyperbolic space do not add up to 180°, so walking in a circle will change the orientation of the map relative to the sword, even though the sword retains its initial orientation.
The monsters of the land are the Draugr. They cannot be killed by the player's usual weapon, but can only be destroyed by the Orb of the Sword. Therefore it is even more important for the player to know how to manipulate the Sword in order to defeat these enemies.
Once 10 or more ancient jewelry have been collected, another orb will start appearing: Orb of the Sword II. This Orb is just like the Orb of the Sword, except that it generates an orange sword, which always points in the opposite direction from the other Sword. Armed with both Orbs, the player can attack two enemies at a time on opposite sides. Once 25 or more treasures have been collected, the two Orbs of the Sword are further strengthened to be able to destroy both types of walls in the barrows, so that it becomes easier to reach the treasures.