Although it is still uncertain whether "Fairy Tail" chapter 503 will come out later this week or early next week, there are now rumors claiming that the upcoming chapter will cast the spotlight on Natsu, who will either transform into END (Ethereal Natsu Dragneel) or into a dragon.

According to reports, fans are now debating as to what Natsu's tumor may mean. While fans have expressed varying interpretations as to what its significance is, two of the most popular theories are either it's a sign of Natsu becoming END or going through the process of dragonification.

Some fans opine that it is possible for Natsu to tap into his inner END in the upcoming chapter 503 of "Fairy Tail," and this will be triggered by Dimaria's torturing of him. 

In the event that Natsu will really connect with his END, it is suspected that it will be Dimaria who will be the first to experience the unparalleled power of Natsu's END.

On the other hand, there are also those who believe that the tumor may be a sign that Natsu will turn into a dragon through the process of dragonification because he has overused his Dragon Slayer Magic.

Meanwhile, apart from the possibly revealing the significance of Natsu's tumor, it is also alleged that the upcoming chapter of "Fairy Tail" chapter 503 will also reveal the real relationship between Eileen and Erza.

It can be recalled that in the previous chapter of "Fairy Tail," Eileen attempted to get the Fairy Heart from Mavis, who only tricked the former using her illusion powers. Realizing that she has been tricked, it is now speculated that as Eileen will hunt down Mavis, and it is at this point where she will come face-to-face with Erza, who is suspected to be either her mother or sister.