Thestral

Bloodthirst 1, Flying, Vigilance
Thestral can be blocked only
by creature which already dealt
damage.
"They're called Thestrals. They're quite gentle, really...
But people avoid them because they're a bit..."
"Different. But why can't the others see them?"
"They can only be seen by eople who've seen death."
-Luna Lovegood and Harry Potter