A ghost can fly/float, and phase through solid rock. Due to its unusual body chemistry, It has no need to breathe. It is humanoid. It has an insubstantial body.
And now the souls of the dead who had gone below came swarming
up from Erebus-- fresh brides, unmarried youths, old men
with life's long suffering behind them, tender young girls
still nursing this first anguish in their hearts, and a great
throng of warriors killed in battle, their spear-wounds gaping
yet and all their armour stained with blood. From this
multitude of souls, as they fluttered to and fro by the
trench, there came a moaning that was horrible to hear.
Panic drained the blood from my cheeks.
The Odyssey, (chapter Lambda), by Homer