Skull

You summon an avatar of death, a ghostly
humanoid skeleton clad in a tattered black robe
and carrying a spectral scythe. It appears in a
space of the DM's choice within 10 feet of you
and attacks you, warning all others that you must
win the battle alone. The avatar fights until you
die or it drops to 0 Hit Points, whereupon it disappears. If anyone tries to help you, the helper summons its own avatar of death. A creature slain
by an avatar of death can't be restored to life.