The Satanic tribute is one of four in the Capitol rotunda, along with the Christmas tree, the menorah and a solstice display from an anti-religion group that includes a sign that says, “Religion is but myth and superstition that hardens hearts and enslaves minds.”

The anti-religion group has been part of the holiday display for several years but has not drawn as much controversy as the Satanic Temple, Mr. Druker said. His office has received only a few complaints, he said, but some of them were “vociferous.”

“People feel strongly,” he said. “They say, ‘Satan is evil, how could we do anything that endorses him?’ And that wasn’t the intent.”

Religious groups and conservatives have been irked by the tribute. Some see it as a mockery of their beliefs, while others see forces at work that are larger than the First Amendment.

On Twitter — a veritable hellscape of its own — Illinois Family Action, a conservative group, said defenders of the tribute “fail to realize that the little baby in the manger has CRUSHED Satan’s head and the gates of hell will NOT prevail.”

But the Satanic Temple, which describes itself as “a nontheistic religious organization determined to halt the dangerous encroachment of theocracy into American government,” says it does not want the gates of hell to prevail.

In fact, the group says it does not “believe in the existence of Satan or the supernatural” at all.

“We do not promote a belief in a personal Satan,” the group says on its website. Instead, it refers to a “metaphoric representation” of “the literary Satan” found in the works of the writers John Milton, Mary Shelley, William Blake and Anatole France.