In 'My Singing Monsters', Ethereal Monsters are a breedable class that can be bred using a Quad-Element Monster and a Triple-Element Monster. They are challenging to breed, with a success rate of approximately 1%, which increases to 5% during Ethereal Breeding Bonanzas. Most of the time, the result will be a Triple-Element Monster of the same type as the parent. For efficient breeding, use the 3-elemental monster with the shortest breeding time and employ egg zapping to speed up the process.