What does these sentences mean?

These texts are quite baffling. I can understand some of them.

The undisguised open mouthed attention of the entire party was fixed on the homely negative personality of Mr. Cornelius Appin. Of all her guests, he was the one had come to Lady Blemley with the vaguest reputation. Sometimes had said he was "clever." and he had got his invitation in the moderate expectation, on the part of his hostess, that some portion at least of his cleverness would be contributed to the general entertainment. Until tea-time that day she had been unable to discover in what direction, if any, his cleverness lay. He was neither a wit nor a croquet champion, a hypnotic force nor a begetter of amateur theatricals.

The undisguised open-mouthed attention of the entire party was fixed on the homely negative personality of Mr. Cornelius Appin.

Everyone in the party looked at Mr. Cornelius Appin with their mouth-opened because they feeling amazed?

he was the one had come to Lady Blemley with the vaguest reputation.

I don't know what "vaguest reputation" is like

he had got his invitation in the moderate expectation

He had got an invitation from Lady Blemley?

What is "moderate expectation"?

on the part of his hostess, that some portion at least of his cleverness would be contributed to the general entertainment.

He might be into the general entertainment.

Until tea-time that day she had been unable to discover in what direction, if any, his cleverness lay. He was neither a wit nor a croquet champion, a hypnotic force nor a begetter of amateur theatricals.

She doesn't know whether he's genius or not? If he was a genius, he would be either a wit nor a croquet champion, a hypnotic force nor a begetter of amateur theatricals?

I don't know what is "hypnotic force" and "begetter"