Chapter 2: Eclipse Gate, Celestial Mage and the Black Wizard
4 years later
Natsu's mark of the fire god now has a few new changes it still has the flames representing the magics he knows of but now each one that he has mastered has a picture of the creature who taught him such as purple (Demon/devil), crimson(dragon), and blue (Phoenix) white (Fairy)and black (God) all of which (besides God slayer magic) have been mastered. The two dragons also changed a bit while one is still black the other is now a crimson color with a crown above its head signifying Natsu's mastery over fire dragon king slayer magic.
With his outfit being the same as before except now he has a white scaly scarf courtesy of Igneel and a Celestial spirit mage who is helping with the eclipse plan to send the dragon slayers 400 years to the future while their dragons seal themselves inside them to prevent the dragon seed from turning into dragons like Acnologia.
Natsu and Igneel are on their way to meet up with everyone involved in the plan and since Natsu is protected from the side effects of slayer magic by the fire gods mark, Igneel along with the rest of Natsu's teachers will seal themselves in a pocket dimension that only Natsu can access courtesy of the God of Fire in order to help Natsu when he needs it.
Natsu and Igneel arrive at the designated meeting spot and see Zeref and Anna Heartfilia who is the Celestial Spirit Mage who is helping with the eclipse plan waiting nearby a massive gate. As Natsu approaches Anna and Zeref time freezes around Natsu and then the zodiac spirit Leo the Lion or Loke as he knows him appears before Natsu and says "By order of the Celestial Spirit King after the Eclipse Gate closes Natsu Dragneel will be pulled into the celestial spirit world where he will be taught Celestial Slayer Magic and Fire god slaying magic by the Fire God and the Celestial Spirit King." he then returns to the spirit world and time flows normally.
Soon after they're done greeting Zeref and Anna, 4 dragons fly down with a child on each of their backs, each of which are asleep. Soon after landing they are introduced to Natsu by Igneel; they are Grandeeney the Sky Dragon, Metalicana the Iron Dragon, Weisslogia the White Dragon and Skiadrum the Shadow Dragon.
Grandeeney then asks Igneel "Why is Natsu awake was it not the plan to send them through time while asleep so as to avoid them asking questions" Igneel then uses a telepathic link with the dragons to explain Natsu's situation as well as the fact he has the mark of the Fire God.
Anna then proceeds to open the eclipse gate and then the dragons along with their slayers go through it when Igneel and Natsu go through they are brought to the celestial spirit world.
Year Unknown: Celestial spirit world
In front of Igneel and Natsu stands a tall man with crimson red hair, piercing yellow eyes and robes made of flames, standing next to him is the Celestial Spirit King and the 12 zodiac spirits as well as the thirteenth zodiac Ophiucus.
The man in the robes then says "We finally meet face to face Natsu." Natsu instantly recognises the voice as the God of Fire.
Natsu smiles and says "Yeah nice to finally meet you in person. By the way, what's your name you never did tell me?'' The god smiles in turn and states, "That's because as one of the four Primary Elemental Gods i go by many names however if you'd like you can call me Ignis" Natsu then says," Ok Ignis. By the way, why are we here? Loke said something about training?"
The Spirit King then answers, "Yes we are here to help you prepare for the future also you should know that when we are done you will be transported back to where you were on the 7th of July 777 at the same age as that day in the old timeline."
Ignis then states "There'll also be some changes to the timeline as the celestial world is given more freedom when it comes to time travel. All the zodiacs will remember the old timeline as well as their master who will be your mate, Lucy Heartfilia.'' This caused Natsu to blush and hide his head in his scarf which caused everyone in the area to start laughing as they all knew the energetic and childish dragon slayer of the old timeline but have never seen him react like that.
As you might expect Ignis is the first to recover and states "that reminds me if you have any other magics, you'd like to learn let us know and we'll try and get a book on it for you i would recommend learning Requip magic and a magic called Soul Telepathy it will allow you to communicate even from long distances with anyone you know including me or the spirit king"
5 years later
Natsu has now mastered all his slayer magic including his newly acquired fire imp slaying magic which is more focused on setting magic traps. Since imps typically aren't very trustworthy, Ignis had to teach Natsu instead. Natsu has also learnt Soul Telepathy, Requip and started learning to combine magics so far, he can only combine 2 at a time.
He is currently way stronger than he was in the old timeline, but he was still nowhere near Acnologia's level. Ignis told Natsu that his best bet for defeating Acnologia is to develop and strengthen his curses since Acnologia can consume all magic. His best bet was to use something that wasn't magic such as the powers he had as E.N.D.
So that's what Natsu's currently working on currently he has developed 5 curses on top of his cursed flames and the curses used by Tartaros they are called.
Void Rift, a teleportation curse with the drawback he must have visited the target place before,
Shapeshift curse it allows him to alter his form to whatever he can imagine,
Nullify curse allows Natsu to nullify any spell or curse weaker than the Nullify curse (basically the stronger the spell or curse the harder it is to nullify, if its stronger it won't nullify it)
Erosion curse allows Natsu to erode a mages magic container making them a lot weaker however the target must be magically weakened first.
Illusion curse allows Natsu to create illusions that are perceived by all 5 senses.
Natsu also wanted to make a type of absorption curse however since curses and magic are fundamentally different, he is having trouble using curses to absorb magic. Nullifying it or eroding the magic container is possible since those aren't trying to combine the powers of curses and magic.
While curses feed on negative emotions to work, magic feeds on a mages magic power which typically is incompatible with demon curses the only reason Natsu can use both is because he is a human revived as a demon or Etherious in fact demon slayer magic unlike most slayer magic was created by both humans and demons working together resulting in a magic equivalent of curses.
Natsu decided to take a break from curses and started trying to learn magic seals which would help with his training and controlling his power if he gets emotional the seals he is working on are actually a form of phoenix slaying magic as that magic is particularly useful for enchantments and seals the seal he is currently trying to master is a gravity seal to help increase his speed by weighing himself down with gravity while training he starts small with a 2x weight increase he draws a magic circle on the ground with chalk and stands in the center and channels a little bit of magic into it the magic circle starts spinning and shrinking rapidly while moving towards Natsu's back where it sits and the effect is instantaneous he feels a lot more sluggish and is struggling to move as his whole body feels heavy. After a while he starts adjusting and can move, he then starts his routine morning exercises.
1 year later
Natsu is about to be sent back to where he was on July 7th x777 in the old timeline the past year he spent mostly learning as much as possible about the creatures whose magic he wields including languages and culture among other things his mark he got from Ignis is now complete on top of the purple, crimson, blue, white and black flames, he also has Gold(celestial spirit) Green(Fire Imp) all of which have a silhouette of the respective creature.
He bids farewell and heads through the portal of flames Ignis opened and finds himself somewhere familiar.