the Mikaelson family & now Elijah Mikaelson, Amalia Dracula of vampire snake duchess both married

The "Elijah Mikaelson is married to a duchess" trope
In fanfiction, it is common to explore alternative histories for the Original family. In this scenario, Elijah, the noble and honorable Original vampire, has an established history as a noble, which is expanded to include a duchess as his wife.
Characters involved: While the specific duchess character is often a fan-created Original Character (OC), the plots frequently involve canon characters like Klaus and Rebekah as part of the married couple's lives.
Common plot points: These stories often occur in a historical or contemporary AU. The duchess might be a powerful supernatural being in her own right, or a human who has married into the supernatural world.
Examples: A fanfiction titled Duchess Mikaelson features Elijah married to a powerful witch named Teresa Mae "Tess" Mikaelson. Another work, The Governess's Secret, focuses on Klaus being a duke, but the aristocratic themes overlap.
The "vampire snake" trope
The "vampire snake" element is not directly linked to a specific Mikaelson fanfiction but likely draws from separate supernatural themes found in fanfiction or broader folklore.
Source of the concept: This specific creature combination is most likely a creative mashup of different supernatural elements, where a vampire also possesses the characteristics of a snake (e.g., venomous bite, shape-shifting).
Elijah and snakes: The closest connection to Elijah is a character named Viktor from a non-canon fanfic wiki entry who is loyal to a character called Luis "The Snake" Ramirez. However, this is not a prominent or widespread trope for Elijah himself.