Majora's Ocarina is the Level 3 weapon in Skull Kid's Ocarina moveset in Hyrule Warriors and Hyrule Warriors Legends. Its design is based on Majora's Mask and befitting dark power of that Mask it has a Darkness Elemental Attribute.
Interestingly, its seems to alter appearance of Tatl and Tael's aura slightly, indicating its dark power may be corrupting and/or empowering them.
Majora's Ocarina + appears as Skull Kid's Level 4 Ocarina in Hyrule Warriors Legends. It is basically a stronger plus version of the Level 3 Ocarina. Like all Level 4 weapons, it has the same design as the Level 3 weapon it is based on.