President-elect Donald Trump attended a lavish costume party Saturday night at a Long Island mansion owned by a top campaign donor.

The “Heroes and Villains” party was held at Robert Mercer’s Owl’s Nest estate in Head of the Harbor, west of Stony Brook.

Trump’s motorcade arrived at the mansion about 8:35 p.m. He was expected to stay for about an hour.

Also there was Trump’s White House senior counselor Stephen Bannon and senior aide Kellyanne Conway.

Trump went as himself, wearing his usual business suit. Conway was dressed as Superwoman.

Conway tweeted: “Honoring the ultimate hero at the Mercer ‘Heroes and Villians’ (sic) party on Long Island. Crowd thrilled w/ surprise!”

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Mercer, 70, is CEO of Renaissance Technologies, an East Setauket hedge fund. Along with his daughter Rebekah Mercer, he helped finance Trump’s campaign.

Rebekah Mercer was recently named to Trump’s transition committee.

The mansion, which overlooks Long Island Sound, includes a $2.7 million model train set and a machine gun collection, according to a Newsday profile on Mercer.

Trump’s sojourn to the party was his only expedition on Saturday outside the Manhattan skyscraper that bears his name. He is expected to lie low the rest of the weekend, before returning to holding transition meetings in New York on Monday and on to the next stop of his “thank you” tour, in North Carolina on Tuesday.

Trump and his associates did not answer questions from reporters outside the estate Saturday night.

With AP