What happens between Liliana and Richard in the woods?

Liliana has brought an orb and explains that it is used to amplify power. Liliana also warns Richard that the power will make him feel as if he is dying, but he must trust her. Richard does begin to feel as if he is dying and then he hears Liliana telling the dark creatures in the woods that they can have what is left of Richard. Richard breaks the hold of the orb, and Lilian pulls out a dark sword and they begin to battle. When Richard kills Liliana he hears a clap of thunder and knows the Keeper has taken her.