The word brimstone is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 16
Highest Scoring Words With Friends™ Play In The Letters brimstone
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Seven Letter Word Alert: (23 words)
benmost, betrims, boniest, bromine, bromise, bromite, entombs, mentors, meronts, minters, mobster, moisten, moister, monster, mortise, norites, orients, remints, sorbite, stonier, timbers, timbres, triones