Answer: Hypnagogic
Explanation:
Hypnagogic is type of hallucination that is felt by people usually before time of sleeping.It can disturb the sleeping person and cause anxiety or stress due to sudden wakefulness. Some mental process takes place in mind in form of visual effect,sound, sensory effect etc.
According top the question,hypnagogic hallucination is experienced by the person who is about to fall asleep but suddenly felt hallucination of falling down from stairs which drags him towards wakefulness.