Mortheus's prison

When you heal 10 health, Transform Mortheus's prison into Mortheus the first
Mortheus's prison can't be exiled and can't be
put into the graveyard
Fear the prison. Many of us have died getting this into
our posession, and keeping it out of the hands of the
beasts that want it. Fear what lies inside, for if it is
released, it could mean doom for us all.
-Unknown Priests Journal