She vowed

Blood spills gently from her neck
As his lips caress her skin
She steels a part of his soul
As he reveals the demon within

He drinks his elixir
And takes away hers
To live the life of death
He thought he would prefer

But as he takes another
And leaves her there to die
The last remaining emotion
Shakes his body as he cries

Love is that emotion
He will feel it forever
Because that precious girl
Vowed to stay with him forever