There was a sudden movement behind them.
Gilderoy Lockhart's knees had given way.
"Get up," said Ron sharply, pointing his wand at Lockhart.
Lockhart got to his feet — then he dived at Ron, knocking him to the ground. Harry jumped forward, but too late — Lockhart was straightening up, panting, Ron's wand in his hand and a gleaming smile back on his face.
"The adventure ends here, boys!" he said. "I shall take a bit of this skin back up to the school, tell them I was too late to save the girl, and that you two tragically lost your minds at the sight of her mangled body — say goodbye to your memories!"
He raised Ron's Spello-taped wand at Harry and shouted, "Obliviate!"
The spell didn't backfire or work like it should, but had a whole new effect instead. Instead of erasing Harry's memories, it gave him some.
The memories of his past life.