Nightsteed of Gavony

Impurity (This creature cannot be targeted by non-
black spells or abilities. This creature cannot
have counters placed on it.)
Whenever Nightsteed of Gavony attacks or blocks, sacrifice another creature or land.
"These are darken days. I once saw a horrid thing that looked upon me. I knew it was once different, now it is
but a husk of its former self, twisted into something it
was never intended to be." -- Gavony Sentry