“A Thestral,” Alexander repeated. “It’s an invisible winged creature which pulls along the carriage.”
“But how can they be invisible? How do you know it has wings?”
“Someone can only see them if they have witnessed death,” Dimitri explained.

Zhenya suddenly felt very fearful. “Witnessed d..death?” she asked, gulping loudly.
The men nodded together.
“How… have you seen them?” she asked.
“My sister was killed right before me,” Alexander said simply. Zhenya had known this.
“My friend’s grandfather died in front of us. He had a heart attack, as the muggles called it,” Dima said. Zhenya had never known this.