I finally figured this game out lol

cat, eat, crate, rest, create

monsters 

I think it is just make five new words? I like more if I can. Stretch the wrinkled brain some, lol!

stem, roster, men, mons ( medical term), some, ton, son, sot

Fairies

Fair, far, air, raise, iris

that was hard

country

County, try, count, no, you

 beautiful 

Be, bit, at, bet, fat

fantastic 

Fan, ant, tan, static, tin

Marvelous 

Mars, soul, arm, rave, so

planetarium 

Planet, plane, plain, net, art

artifacts 

Fit, fat, fart, tact, tart, tar, cat, cart, 

Automobile