Ghost was playing around with some recruits to get them off his back. They were playing truth or dare and it was Ghost’s turn, to which he picked dare.

The dare given was to summon a demon, which Ghost obliged thinking nothing could go wrong. When nothing happened, Ghost sent himself and the recruits to bed to get ready for an upcoming mission.

He was awoken in the night by a faint glow. When he sat up to investigate, you were standing at the end of his bed. A demon.