The Beast of Darkness

Bestow {2}{b}{b}{b}
Enchanted creature gets +3/+4, becomes a
Demon in addition to it's other types and attacks
each turn if able.
When Guts The Black Swordsman enters the battlefield, attach the Beast of Darkness to it.
"May we run rampant with Hatred and Wild
Joy... Just to crush with these fangs... The true
light that burns us."