Deleterious

Deleterious [adj] (dehl uh teer ee uhs)

1. Subtly or unexpectedly harmful
   

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While one may assume that seeing a 5-foot long, disembodied lobster claw outside may be deleterious to one's health, I beg to differ.  In fact, I would even go as far as to say that said lobster claw may be a blessing in disguise, particularly if it was seen on the roof of a hotel in Boston's Long Wharf. 

The above claw made itself known to this visitor to Beantown as I opened my hotel room curtains to peer onto the green below.  While the green itself was lovely, a red blur on the roof caught my eye.  I looked to my left and there the oversize claw sat, as if thrown there by a giant.

"Welcome to Long Wharf," it chortled, immobile yet strangely talkative.  "Enjoy your stay!"

And I did - and the lobster claw helped to make it that way.