oneiro-, oneir-, oniro-, onir-, -neir-

(Greek: dream)

onirogenic
Giving rise to a dreamlike state.
oniroid
Like or resembling a dream.
paroneiria, paroniria
Morbid dreaming; disagreeable, or terrifying, dreams.

Related "sleep" units: dorm-; hypno-; letho-; narco-; somni-; sopor-.