I was trying to only spoil some of it, here u are spoiling everything lolPartly this but not all of it. You guys want heavy spoilers then at your own risk.
act 1 spoilers: Tinasha is pretending to be in love with Lanark (this sissy looking guy). He happens to be her former fiance from 427 years ago when the magic kingdom of Tuldar still existed. The thing is, it is a sort of meritocracy where magic power and skill dictated who the king would be and despite being a commoner, Tinasha was one of the candidates with Lanark, a royal from Tuldar was the other. They were made fiancé and fiancee because no matter which of them would be ruler the other being the opposite genre would guarantee strong heirs. Regardless Tinasha came to love Lanark, as a sibling mind you. She had no one else because children with such power were always taken from their parents at birth to be candidates to rulers.
However the Jealousy of Lanark towards Tinasha's power made him plot something nasty, a dark ritual in which he would sacrifice all the people from Tuldar and store their magic essence which is basically their souls into the five lakes to then absorb it himself and acquire unimaginable power. The main catalyst being Tinasha herself, he lures her into a temple where accomplices mages prepare a ritual. To make a long story short, Lanark will literally cut her open and make the ritual except Tinasha manages to take control of the magic and absorb it, becoming a witch in the process with Lanark escaping and Tuldar disappearing overnight. Jump to the present, Tinasha needs Lanark alive to make him lower his guard and tell the names of the five lakes so she can release the souls of the people from Tuldar from them. Remember how curses work in this world, the one casting uses arbitrary words to attach them and give power to it. So yes, in a way she betrayed Oscar but realistically she wanted both to keep him safe and prevent him from killing Lanark there and then.
About the end of act 1: Tinasha and Oscar will get married after defeating a witch and that's where the Eleterria come into play once again. Eleterria are two spheres that can basically do what it's impossible in that world, travel to the past. These spheres are the ones Valt and Myralis (those two from the demonic beast lake arc) are after. Well for many reasons Oscar and Tinasha will end up holding the spheres.
One month after their marriage they are living a happy life as king and queen of Farsas. However one of those days Tinasha went back to her tower to clean all of her magic items. Oscar decides to go after her and help her fix the place. While she goes to the kitchen of the tower to cook their food, Oscar finds a bloodied silver necklace which reminds him of what Lanark did to Tinasha 427 years ago. Also he drops an old and plain looking white box which opens to reveal a weird, rune filled sphere no bigger than a golf ball that he holds out of curiosity. Tinasha comes back just to witness Oscar, the sphere and it activating itself. While trying to scream at him Oscar disappears and with him the whole world because Eleterria sends him 427 years to the past.
You see, in UM timelines doesn't exist as in the definition of branches. There is only one timeline and if somebody tramples with it, what came after will cease to exist to let the story be written anew. Also as I explained earlier, time travel is impossible in that world... that is unless what makes it happen isn't a thing from that worls. Eleterria, two spheres from another world...
So Oscar will find himself meeting 13 yo Tinasha, telling her about being her husband 427 years in the future, meeting young Lanark although while hidden by Tinasha's magic and finally finding one of the Eleterria from 427 years ago. However just when he plans to return to his Tinasha in the "future"... his always brave heart pushes him to do what that bloodied necklace reminded him to do... save Tinasha from Lanark's ritual knowing too well by doing so, he will cease to exist... and so it happens. Basically this Oscar ceases to exist, preventing Tinasha from suffering, allowing her to naturally be queen of Tuldar, saving the magic Kingdom of Tuldar, killing Lanark and ending act 1 of the story.
Of course as an interlude, Tinasha ruled Tuldar for five years until she disappeared after being defeated by Travis, the king of demons who fought her, defeated her and spared her life on a whim. Why? Because he was bored of course. Also because Oscar prevented her from becoming the witch of the Azure Moon so she was way weaker than the Tinasha from act 1, the one most of you know. Travis out of boredom tells her, while she believes she is about to die and call Oscar's name one last time to tell him about this Oscar she called in her "last moments" and just for the heck of it heals and suggests her to sleep for 427 years until she meets her husband to be.
Act 2: prepare to cry
well Oscar prince of Farsas and his aide and close friend Lazard step into the magic kingdom of Tuldar, 425 years after Tinasha put herself to sleep. He was cursed by the witch of silence yadyada you know the rest. The king of Tuldar (which will surely make your blood boil) tells him nobody can actually help him, offering as a last resort try a sealed tomb in the palace of Tuldar, believed to be the resting place of the strongest queen Tuldar ever had. But nobody could ever open and by extension step on it in centuries since found.
Oscar accepts and to everybody's surprise it opens to him without issue. However only Oscar can enter because there is a super strong barrier that won't allow everyone else. There he meets a girl with twin tails, one of Tinasha's demon servants and a red sleeping dragon, Nark, Oscar's dragon that immediately recognizes him.
I forgot to say this, Naark the dragon also traveled to the past with Oscar (he was with him when the Eleterria activated).
The demon girl greets and prompts him to go further ahead where a garden with a beautiful bed are and a black haired girl sleeping on it. She is Tinasha and she wakes up to the touch of a mesmerized Oscar. This is how the cursed prince and the (now) strongest former queen of Tuldar meet yet again.
Remember all of this is for the curious. So anyway Tinasha will take Oscar's role from act 1, trying to make him marry her while he will avoid it all the time because of the sob king of Tuldar.
The king claims Tinasha is a treasure of Tuldar, basically blackmails her to be queen once again and marry his own son.
Tinasha will temporarily go with Oscar however for six months while studying and trying to solve his curse.
So act 2 introduces Valt and Myralis as the true villains of the series, they will always and I am not joking, always be one step ahead of Tinasha and Oscar. Many characters and event from act 1 will happen and appear again but in different circumstances. Remember Tinasha isn't the witch and she is weaker in comparison now, Oscar is more mature but very stubborn about rejecting Tinasha to avoid a diplomatic confict with Tuldar and Tinasha being sad about the fact this is not the Oscar that saved her (and his rejection).
Well many things will happen. Oscar and Tinasha will get engaged but never marry in this act because...
Valt and Myralis will succeed in convincing Tinasha to get the Eleterria from Farsas and Tuldar and make her cooperate to destroy them both.
You see, Valt's family line can remember every time the world is reset by Eleterria. However being in that loop is causing him and the world to fall appart. Add to that in every time his beloved Myralis dies and ever since Oscar created a new point (where he saved Tinasha)... Valt's soul and mind are getting weaker.
So Tinasha and Oscar face each other, Tinasha betraying Valt in the last minute and Oscar pushing her into the subterranean lake of Farsas castle, the lake of silence, place of appearance of Akashia the anti magic sword. This lake has the same properties as Akashia.
While Oscar fights Valt, Tinasha jumps into the lake with the Eleterria and appears thanks to the sphere asking her for her happiest moment to be in Oscar's bed.
(Yeah this is a 3rd Oscar. A new timeline and the one with the world of act 2 disappeared at this point).
It so happens that in this story, Oscar and Tinasha are already married. Tinasha cries and tells Oscar what could be a crazy story to him yet he belives in his wife.
now let me explain why at this timeline. To activate the Eleterria you need the will to do it, determination and the "longing for a specific time which carries an emotional power" to the bearer. Tinasha before falling into the lake of silence regretted not being able to marry the man she loved across time in that time of act 2. That is why she appeared in a timeline where they were already married. Just like Oscar regretted not being able to save Tinasha from Lanark 427 years ago in act 1 and that made him travel 427 years into the past.
Well, Oscar being the gigachad he is, immediately gets up with his wife and takes her to the treasure vault in Farsas to get the second Eleterria from that timeline (plus the one Tinasha carried with her). Both of them hold Akashia and destroy the Eleterria once and for all...
In the mist of disappearing both Eleterria seek refuge into the bodies of Oscar and Tinasha, turning them both into outsider artifacts just like Eleterria or akashia. And so their new tragedy begins. They can't go back in time anymore but they become sort of immortal:
They can die, but they will be able to reincarnate as new beings however, they don't necessarily reincarnate in the same time period or even close to each other, also they won't remember until certain event or time passes and they won't know who the other is until both find the other.
For example, Oscar will die many years after being king and queen of Farsas while destroying an outsider artifact. Tinasha will mourn him and look around the world for him until Oscar reincarnates as a boy names Reiju, seventy years after his death.
Also before all this, they learned tere are over a dozen outsiders artifacts (like Eleterria) and they have to destroy them if they want to find peace. However almost every time they fight an artifact, one of them will die leaving the other grieving and leaving in depression for decades.
And so the story continues cause this has a sequel currently being written.
Ya eleterria rlly fucked the timeline into sth unrecognizable huh