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Additional duplicate: Did the Death Eaters Know Voldemort Was a Half-Blood?
In Harry Potter and the Chamber of Secrets, we first hear the name Tom Riddle. Until the end of the book, Tom appears to be good, although mysterious. In the school, there is even a trophy with his name on it which he won for special services to the school. Then when Harry goes to the Chamber of Secrets, we find out Tom is actually Lord Voldemort.
Now, why would the trophy for Tom Riddle still be up in the school if it was well known that Tom was Voldemort? But at the same time, it wasn't a secret. Dumbledore knew who Tom was. Slughorn knew who he was. Helena Ravenclaw did too as did a few Death Eaters who went to school with him (and probably a few more.) In fact, Lucius Malfoy knew the diary he had which he sneaked into Ginny's bucket belonged to Voldemort, and it had the name Tom Marvolo Riddle on it. So he must have knew his true name. So how many people knew? There must have been stories written about him after he was presumed dead following the murder of the Potters. Surely one newspaper then tried to find out more about who he was and where he came from.
But even after Harry knew, and he presumbly told a few friends, we never hear anyone other than Harry and Dumbledore call him Tom. I understand that Voldemort was his name then, so it made more sense. But how many people really knew the truth about Tom?
For that matter, if the Death Eaters knew he was Tom Riddle, then they must have known he wasn't Pure Blood. There were probably Half Blood Death Eaters too, but wasn't it a bit strange to Pure Blood Death Eaters that they were being led by someone who wasn't? It couldn't have been too big secret, since Dumbledore said he went after Harry and not Neville because Harry was a Half Blood. But was it just Dumbledore who thought of that? Did the Death Eaters know this is why he choose to go after Harry? And again, Lucius had the diary. At the least, he knew his true name. Didn't he ever do any digging? Or was Tom being a descendent of Slytherin himself enough to ignore his Muggle family?
So basically, was it well known that Tom Riddle was Voldemort and did the Death Eaters know he was a Half Blood?