Spoiler- Suggest You don't read, but you can do as you like

Like It says in the title I would suggest you don't read this, but this will contain a few spoiler regarding the story, Isaac's powers and maybe what he will do in the future. 

I will update it once in a while or if I change anything.

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I will start by saying that Isaac isn't a Hybrid but a Tribrid. His most prominent side being the wolf, followed by witch and than vampire. 

This came to be by him being a descendent of Inadu, AKA the hollow, which in this ff had a child with a man from her tribe before she was killed. The son inherited her talent for magic, but didn't tap into his powers as he was he was left with his father at a nearby tribe.

About 480 years later, Isaac's father, an untriggered werewolf-witch hybrid, (His mother was an untriggered witch of the Inadu bloodline and father a werewolf of the South-East Atlantic pack) the last living offspring of Inadu, Fell in love with a widow who had a young daughter, and you can guess the rest...

Anyway, even before he triggered his curse, Isaac could feel his wolf part, even if only slightly. After he triggered the curse, he meditated like he did once in a while before, and in the process gained his first unique ability.

Every werewolf has 'a wolf' inside them, this wolf remains dormant except for during the full moon, or when the werewolf feels intense emotions or has an extreme change in state of mind. 

In the meditation state, his wolf senses are enhanced by his magic naturally, allowing him to create a 'domain' with the radius of a few kilometers in which he can feel everything. In that state, he could also see and talk to those on the 'other side'.

When he drank the wine laced with blood and the immortality spell, if he was a normal human, or even a normal werewolf, it would have just left his system after awhile. But by following his routine and meditating every day, even though he couldn't enter the state of meditation.

This was actually caused by his wolf, which with the help of the magic circulated by the meditation, managed to 'consume' a large part of the magic within the wine and also preserved it, allowing it to stay inside Isaac's body. 

His wolf grew stronger and stronger, feeding on the magic in the spell, resulting in its growth in size and strength, as well as the disappearing of some parts of the curse/spell, which didn't apply to Isaac.

Eventually, only the curses relating to the sources the spell were drawn from remained which were the sun, the white oak tree, flowers at its roots and the blood. The rest disappeared.

As for the strengths, they were spread amongst those two species. The werewolf growing stronger and stronger, while the vampire grew weaker and weaker, when he 'died', a balance was set, but the rest of the things remained. 

So as a result, human copulation had become werewolf commanding as well as animal compulsion. His speed and strength as a werewolf were absurdly higher, while as a vampire, he was about equal to other vampires of similar age, and slightly weaker than the originals. 

And lastly, as a most werewolf, his body actually remained alive, retaining all human functions, including reproduction, and the ability to temporarily feed on meat, to replace blood. As long as he ate meat. even without blood, he could remain undesecated and fully active for even ten year, though the hunger for blood would be excruciating. 

During the transformation, with the spell being bound to the sun and the white oak tree, Isaac's wolf, which had already started to draw from the power of the sun resulted in it already not being bound to the moon, so when he turned it was no longer a counter to the the weakness of the sun and because of that he could still be burned by the sun even as a Tribrid.

On the night of the full moon, he was about to Transform finally into an enhanced, but mortal, werewolf able to turn at will, when Ayana's spell, which was bound with the power of the moon to his transformation, was triggered and the moment he and the wolf were about to assimilate, it caused an overflow of energy in his veins, eventually causing all of them to explode, which was enough to kill him.

With the spell of immortality taking what the user liked most about themselves, like the Mikaelsons enjoying their popularity in another continent and their sense of family. They now were no longer able to enter the houses of their friends uninvited, and were split as a family(though not directly, it was still related none the less.)

Meanwhile Isaac, didn't have anything in his life he truly enjoyed, except for his sister, who he kept away from for her own good, but she died in Elijah's hands before his memories returned. He didn't even meet her child. And so, he could still enter houses uninvited. 

Another is the ability to create more of his kind. By biting a human being, the werewolf venom spreads into them, changing them. Like a snake, once not biting out of self-defenses and fear, if he knowingly tried, he eventually could control the amount of venom in his bite, creating dry-bite which won't turn anyone. Or kill-bites, which will act like poison, killing the target(Isaac's venom specifically can even effect the originals, and if it is untreated over a long period, or gathered in a high enough concentration it will kill them.) 

Only the werewolves turned by Isaac can create more, until either their offspring, beta or killer takes their place upon their death, becoming the new Alpha(similar to TW). Just like Isaac, they can choose if they want to turn the target or not. 

Nature is fair... for what one gains, one loses, and for what one loses, one might gain.

Important to note, is that all immortals have to drink blood in the TVD universe, so to be immortal, one has to be at least part vampire(That is if we consider vampires as creatures with the need to consume blood to survive.) 

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There will be several Original species But they are all integrated in the context of legacies. That is to say, the world remains the same, its like a part of the world that the characters in the show never knew about.

Elves, Dwarves, Fairies, Goblins, Minitours, Satyrs and more, all exist, but were, in the original timeline, either consumed by Malivour, or remained hidden from the rest of the world. 

Some like the elves and fairies, are hidden by magic. While dwarves just kept to the underground for example.

He will come across several of those, and they will be integrated into the story. 

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All of his allies, pack members, vampires, witches and every other specie, will take part in an organization he creates, name 'Senate of The Seven Seas.'

This is basically a representatives council, giving a voice to every faction. Though some are given a little more say than others based or strength, abilities or even connection to Isaac, as he himself holds veto rights as well as the final say in every decision. 

The Senate gathers every five years, and every proposal and decision are reported to him, allowing him to manage the bigger picture, while not being directly involved when he doesn't wish to be. 

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To make another thing clear as day, He is stronger than the originals, much stronger, But only in wolf form. In human form, he is around the power level of any other vampire of his age, that is if you don't add his top notch combat skills.

He practices the sword for hours daily for basically all his life. Not to mention he was already an expert combatant even in his last life. With his experience, over powering someone a little stronger is not only possible, but expected. 

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Another thing, Isaac isn't actually dead. At least his body isn't. Unlike vampires, which are reanimated corpses, Isaac is more like Silas. He had actually died, but it more like 'his wolf' turned immortal at the exact moment the spell killed him. As a result, he only partially died, and what actually revived him, wasn't directly the magic, but the wolf using it to 'Jump start' his body.

This allowed his witch side to remain active, even after 'death'. This is also what partially allowed him to access his past memories. This life was the 'gift' he got for his struggles, but it also came with losing all memories. By dying, he was to regain his memories and reincarnate again, but since his didn't actually die, he returned to his own body. 

As explained, this, the wolf drawing on the power of the spell, the spell itself. All of those made Isaac what he is. But in essence, one might just say, that instead of Tribrid of werewolf, vampire and witch, He is in fact, a hybrid, but of a witch and something else, something that had never been seen before, a sort of an empowered werewolf. 

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Ideas- opened to discussion

-Daylight Tattoo- Vampires in the show are seen to have tattoos, and they aren't there since the beginning, meaning in the show(even though I guess for the writers its just a plot hole) there is a way for vampires and werewolves to get them. (See Klaus for example, in season 2 he has no tattoo and season 4 he had the birds on his left arm.)

Sometime, Isaac will see that the probability of losing his ring is a weakness and will obtain his own, a tattoo made by a witch which acts like a daylight ring, but because he is still part witch, and unlike other ones who turned, hasn't lost his connection to the spirits, this ability will become permanent, with even witches being unable to affect it. 

-Isaac's Katana- When it was bound with his blood, the sword got a few magical affects.

1) Poisonous to both Werewolves and Vampires- Isaac's blood if filled with Aconite(wolfsbane) and Blue Verbena(a type of vervain/verbena native to Japan), when his his blood was mixed with the sword, it absorbed those qualities, making every scratch caused by it to weaken both species.

2) Bleeding- Like in games, any injury caused by the sword will be far harder to heal. 

3)Self Restoration- It gained Isaac's blood healing properties, making it never go blunt and even if it cracks or brakes, it will repair itself. 

4)??? 

This is what I will give you for now, you can Comment if you have any ideas you would like to share.

-Isaac's Venom- 

1)Secretion and concentration can be controlled at will. When secreted on instinct, will have a concentration of one percent.

2)When injected to a human at lower levels, will cause transformation to werewolf, at higher doses, will cause death.

3)Deadly to most species, but has a euphoric effect. One being bitten and injected with the poison at a high enough dose, will experience euphoria before dying from senses overload. At lower doses, acts like any other werewolf poison, killing slowly with great pain. Werewolves are partially immune, allowing them to experience this feeling, yet not die.

4)He is 100% immune to this poison, and any other one, except vervain and wolfsbane, to witch he built a tolerance over time.