What's the noun for thwartable? Here's the word you're looking for.
thwart
(nautical) A brace, perpendicular to the keel, that helps maintain the beam (breadth) of a marine vessel against external water pressure and that may serve to support the rail.
(nautical) A seat across a boat on which a rower may sit.
“Ms. MacLaine plays the thwarter, Bruno's grandmother, who suddenly becomes an ardent supporter of Bruno's desire to wear dresses, an amazing leap for someone who thought opera singing was for sissies.”
“Similarly, Ripley, as the thwarter of the wishes of the godlike Company, proclaims herself as the adversary of this narrative.”
