Power dynamics is another theme. Eric is a powerful vampire and Sookie has her own special abilities. Fanfictions play around with how these powers interact and affect their relationship. Sometimes it's about Eric protecting Sookie with his power, other times it's about Sookie using her gift to help Eric in some way.
One common theme could be the challenges they face as a couple during the pregnancy. Another might be how their relationship changes and grows stronger.
Another theme is the allure of the forbidden. Their relationship is often seen as something that goes against the norms, either in the vampire - human world or within their own communities. This adds a sense of danger and excitement. For example, in many fanfictions, they have to hide their relationship from others. Also, the theme of redemption is quite prevalent. Eric's dark nature often needs to be redeemed in some way through his love for Sookie. In some stories, he has to overcome his past deeds to be worthy of Sookie's love. This makes for some really engaging character development.
One popular 'Dark Eric and Sookie Fanfiction' is 'The Viking's Bride'. It delves deep into their complex relationship in a rather dark and alluring way.
One common theme could be the challenges they face as a couple during the pregnancy. Maybe dealing with how their relationship changes or how their families and friends react.
Love and loyalty are common themes. Their relationship is often tested, but they remain loyal to each other in many stories. For example, in some fanfics, Sookie has to choose between Eric and her human friends, and her loyalty to Eric shines through.
The theme of immortality and mortality is also prevalent. Godric and Eric are immortal vampires, while Sookie is a mortal human. The fanfictions often play with this contrast, like how Sookie views the vampires' eternal existence, and how the vampires see the fleeting nature of Sookie's life. It adds a layer of melancholy and urgency to their relationships.
She might gain new powers. Vampires often have enhanced strength, speed, and senses. Sookie could use these to her advantage. For example, she could better protect herself from the various threats in the world of the story.
Another good one is 'Sookie's Choice'. It explores Sookie's internal struggle between her feelings for Eric and other aspects of her life. The author does a wonderful job of painting a vivid picture of the world they live in, and the interactions between Eric and Sookie are both sweet and intense.