"Ghost" is a term given to a newly discovered being thought to be heavily related to another Realm System.
Material Make Up
These Ghosts have been examined and their make up has been noted. Only three instances of Ghosts have been captured, and shortly after being examined, they escaped.
So far, they have signs of Abberrant Mana, Soul residue and the essence of something not from this System.
The Ghosts are highly hostile, yet can be subdued easily using binding Magic. This suggests they have a physical body, not just energy.
Ghosts were mostly created in the Destiny System, however, the object they're bound to is from another. A shard from the object was broken off with a highly concentrated spell, and was examined. It was nothing like the rock from this System, which is usually infused with highly stable and concentrated Mana. It was completely devoid of Mana, but attracts Mana to it.
Ghosts don't seem to have emotion, but seem to have an ascendant level of intelligence. This was proven through their means of communication, something most humanoid races can't comprehend. With help from a young God, it has been determined they use a series of howling, whispering and hissing noises which sound different to each person who listens.