Ancient wizards return to Hogwarts

Salazar Slytherin was resurrected a thousand years after his burial.
After waking up, he returned to Hogwarts anonymously and reborn, and then he was shocked to discover:
At that time, families who were keen on marrying Muggles or simply being Muggle-born claimed to be pure-blood families.
The lunatic who appeared out of nowhere and pretended to be his descendant became the dark lord that people talked about, using his own banner to promote extreme ideas.
While all kinds of magic spells have become fancy, the bodies of wizards are extremely weak, even the descendants of Gryffindor are no exception.
Slytherin: Voldemort, I think you're a bit extreme - and, how come I didn't know I built a secret chamber in the castle? Wait, you're not referring to the basement where I used to teach, are you? !