melkor leader of darkness

As long as Melkor leader of darkness is the only creature you control he gets +5/+4
When Melkor leader of darkness enters the battlefield destroy all human creatures.
Reveal Ungolianth, The Betrayed from your hand put Melkor, Leader of Darkness on the bottom of your deck any player may activate this ability.
If this card would leave the battlefield, exile it instead, search your deck for a balrog creature and put it on the battlefield tapped, shuffle your deck afterward.