@ecyoj,
Hi ecyoj
Can you assist by posting how many letters is each word and any possible letter you have? I have several answers but don't know if they will fit your grid. e.g.
obsequies= oily, abject, creepy, sycophantic and many others.
monster = ogre, beast, brute, fiend, ginormous and many others.
parasites = flea, leech, epizoon, bloodsucker and many others.