At the end of vol 17 Bell's stat sheet was shown just like at the end of vol 11 after which he leveled up at the very start of vol 12, so it most likely means that he'll be a level 5 by the start of vol 18. Most likely Bell will become a level 6 to finish the book off after his fight with Ottar. But there is also the possibility that Bell becomes a level 6 before his final fight with Ottar if Bell has two major fights.
He would level up to level 6 after the first one, it would be against the Freya familia's 1st tiers (excluding Ottar) which Bell would be ready for after training with loki familia and maxing out his level 5 stats. Then he would run away/recover/hide for a bit (from what I've read, vol 18 will have a hide and seek format so it would make sense for him to do so). Ultimately he will have his final fight with Ottar maxing out his level 6 stats, beating him in the process and leveling up to level 7 at the start of vol 19.
The reason I think that Bell could be a level 6 when fighting Ottar is because if he was a level 5 it would even be a fight, you know? I only came up with this theory after reading Gupnut’s opinion on the matter. He had the idea that Ottar would be the way Bell became a level 7, that Asterios would be the way Bell became a level 8 and that whatever is at the bottom of the dungeon would boost him to level 9, so the fact that Bell would probably be fighting Ottar as a level 5 and not as a level 6 didn’t make too much sense.
To make sure I’m not just talking crap I make a graph like the one Gupnut maked but extended it to level 11. This will all make sense in a second I promise….. :)
The graph aint showing :(
What I’m going to talk about might seem off topic but trust me it’s on topic.
Based on the comments on:
Albert had the power of a level 10 when he fought against the OEBD which is estimated to have the power of el level 11, so to drive it away Albert had to sacrifice his life because he wasn’t strong enough to kill it. In short, Bell has to be even stronger than Albert to have a chance at killing the dragon and staying alive (cuz if he dies I’m gonna lose my shit).
Anyway, in the graph you can see that Bell as a newly level 9 is almost as strong as a newly level 11 Aiz. If we use Aiz as a base we can say that Bell at level 9 has a boost equivalent to around 2 levels. Which would be perfect for what I said earlier about albert. Not to mention that this “He had the idea that Ottar would be the way Bell became a level 7, that Asterios would be the way Bell became a level 8 and that whatever is at the bottom of the dungeon would boost him to level 9” would now also make sense if my theory about Bell leveling up twice with the events in vol 18 is correct.
I also agree with Gupnut about the fact that Bell would probably need some sort of new ability. Maybe Bell can develop argonaut so it covers his whole body and keep it activated for a prolonged amount of time, which would boost his overall power or something.