The Vampire Diaries had two successful spin-offs: The Originals and Legacies. The Originals featured the family of the original vampires with Klaus Mikaelson serving as the main character. Klaus had been one of the main villains on The Vampire Diaries. After discovering that he would be a father, he entered a path of redemption. It was not an easy path, and we watched the struggles that Klaus and his family had for five seasons.
Legacies follows Hope, Klaus's daughter, at the Salvatore School for the Young and Gifted. Rather than redemption, Hope's focus is in trying to understand her purpose. Her family sacrificed a lot for her--their lives, sanity, and independence. Hope feels guilty about the sacrifices her family made, wonders her worth, and grieves the loss of her parents.
A miracle baby for many reasons, she is also the first of her kind: a werewolf/vampire/witch triad. At the end of Season 1, Hope discovers a purpose. As the only triad, she alone can stop Malivore. We end with not knowing her outcome and seeing the other characters forget her since Malivore erases magical beings.
In Legacies, we also have Caroline and Alaric's daughters, Josie and Lizzie, first introduced to us as young twin sisters in The Vampire Diaries. At the end of Season 1, they discovered the Gemini Coven's purpose for them; when they reach the age of 22, Gemini twins merge together; the stronger twin absorbs the weaker one. After our three legacies (Hope, Lizzie, and Josie) discover their intended purpose, what happens next? How do the other supernatural children grow used to their own powers?
What characters from The Originals and The Vampire Diaries should come back to help our legacies out?
Freya
Freya is the eldest daughter of the Mikaelson's. An aunt and mentor of Hope's, Freya is a powerhouse of magic. If anyone can help Hope get out of Malivore, it is Freya. Familiar with other worlds and a natural skeptic/researcher, she would question Hope's lack of being.
She would be suspicious of her brothers' deaths without knowing the reason behind them--saving Hope. In addition, Freya may be able to help the twins. To be perfectly honest, Freya seems almost too perfect for Legacies.
Klaus
Hope learned that Klaus watches over her, wanting to see her happy. It is unlikely that he will stop watching over her and would be happy about her choice.
We also don't know if the erasing of magical beings extends to the afterlife; it could be that Malivore can't erase the memories of the dead. Klaus loves Hope. Being persistent, his spirit would fight to reach out to Freya and inform her of what happened.
Marcel
Marcel considers himself both Klaus's adopted son and Hope's brother. We want to see this close bond explored more. If Hope were threatened, Marcel would be there on big brother duty to protect her. In addition, Marcel cares about kids.
We could see him coming to the Salvatore School to mentor some of the vampires like Kaleb. Marcel could serve a key role in guiding Hope towards a better understanding of her purpose in this world and as part of this unique family.
The Sirens
While Cade killed the Sirens (Seline and Sybil) in The Vampire Diaries, their connection to the twins may be an interesting one to explore. Seline had been their nanny at one time and chose the twins to be substituted for her and Sybil.
This means that our two favorite twins almost became ultimate villains, isolated and denied the intense love of their parents. Bringing these two characters back, albeit briefly, could help strengthen the twin bond that weakened towards the end of the season.
Valerie
Having Valerie do a cameo in the Legacies would be a golden opportunity for the twins. Valerie shares core similarities with the twins: 1.) She was a member of the Gemini Coven; 2.) She is a siphoner. She also is a Heretic. Those three characteristics together make her the ideal person to bring back for a cameo.
Not only can she give the twins needed information about the history of their coven and The Merge, but her Heretic magical background could also prove useful in breaking the curse. We're surprised that Caroline hasn't sought Valerie out yet.
Davina
Although living a happy life with Kol (Hope's uncle), Davina is a powerful witch who escaped death. She also was forced to grow up too quickly by being exposed to a terrifying ritual, all-consuming power, and family/coven rejection/abandonment.
Often a pawn or a tool in another character's quests or revenge schemes, she became a stronger character. Davina could teach all of the witches at the school, and she could help her niece. We need a Hope Rescue Mission. Both Davina and Freya should be the captains.
Katherine
Every time Katherine dies or seems to have been removed from the equation, she returns. The character is a survivor. Drag her to hell; she becomes the queen of hell. Make her human and die a human death; she figures out how to jump bodies. Katherine, a pragmatist, could add some needed tension to Legacies. While generally considered a villain, Katherine has had many hard breaks. The lesson she learned about surviving comes from those breaks. Klaus literally hunted her for most of her vampire life and came to gloat over her dying body. We want to see a twist in that dynamic. What if Klaus had to reach out to Katherine to save his daughter?
While we doubt that Katherine would be brought back, it would be a delight to see actress Nina Dobrev reprise this juicy role for a quick cameo. Though some may prefer Elena, Katherine was the more dynamic character, but maybe not the one you would confide your secrets to or trust in any way. In addition, Katherine could try to rescue Uncle Kai, a much scarier villain than Katherine.
Keelin
As the only werewolf of the Malraux and Aunt Freya's beau, we never saw enough of Keelin in The Originals. However, Keelin's character could be developed more in Legacies. She could work as a mentor to guide some of the werewolf students having a harder time coming to terms with their background.
It would also be neat to see if there were another member of the Malraux clan besides her, someone intentionally hidden from the powers that be. Then the history of the mysterious Malraux clan could be explored.
Hayley
Hayley's stay on Legacies would need to be brief since her character is so engaging that she could easily overshadow the young legacies. We don't think that she should be involved with Hope in the cameo (our tears wouldn't stop) but rather with Rafael. At the end of Season 1, Rafael was left in his wolf state. Hayley and her Crescent Wolves know what that is like. Perhaps through a dream, she could counsel Rafael.
When Rafael eventually tells Hope, she might feel envious and grow more connected to Rafael, leading to a potential love triangle between Rafael, Hope, and Landon. Who doesn't love a love triangle?
Caroline
Hinted at several times by Alaric, Caroline is searching the globe for a way to stop the twins from merging. We want to see Caroline on the show, even if briefly. She loves her children, and Lizzie is especially close to her. Due to her advice, Lizzie starts working on being a better person. Witnessing their dynamic would be great.
In addition, Alaric keeps on telling everyone that he built the school, that it is his school, etc. Caroline needs to put him in his place. The school was a total team effort. Without Caroline, it never would have happened. Alaric, stop taking all the credit. Caroline, in her gentle but firm way, can reclaim that which is hers, and our bet is that she would be able to run the school in a more organized fashion than Alaric. If her patience with Klaus is anything to go by, Caroline should be able to deal with difficult customers.