As nouns the difference between spell and preyer
is that
spell is (obsolete) speech, discourse or
spell can be (dialectal) a splinter, usually of wood; a spelk or
spell can be a shift (of work); a set of workers responsible for a specific turn of labour while
preyer is one who, or that which, preys; a plunderer; a waster; a devourer.
As a verb spell
is (obsolete) to speak, to declaim or
spell can be (obsolete) to read (something) as though letter by letter; to peruse slowly or with effort or
spell can be to work in place of (someone).