[@vancexentan]

The banned or limited powers list will likely grow as I refamiliarize myself with everything, but so far I've got the following list that will be put in the rules section:
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Godslayer Magic - No "dragon slayer but better" things.

Time-based powers - These, when it comes to roleplay, give pretty much nothing but problems. They are often times an "I win" button, on top of just being one of the most difficult powers to roleplay against properly.

Mind effect/control powers - This is more of a heavy limitation rather than ban. I may consider very balanced exceptions. These kinds of powers can easily cross the border into god-modding, controlling another character's thoughts, actions, or feelings. It is very difficult to roleplay correctly and overall is just a nuisance.

"Logia type" powers - Yes, I shamelessly stole that term from One Piece. This basically means any character that can turn their entire body into a non-solid element. Such as someone who can fully become water. These types of powers just provide way too much defensive capabilities. They render the majority of all attacks against them entirely useless, minus a few, select specific weaknesses. This is unfair to the majority of the rp, and will not be allowed.

Mimics/Copycats - No. Use your own powers. Don't just copy other characters in the rp.

Telekinetics - These are also not fully banned, but will be heavily limited as they can be some of the most overpowered for lowest effort. No Ravens.
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Again subject to grow, but that's what is there so far. I'm not wanting to go into specific moves within existing powers at this time, as I'll judge every character sheet individually. But I will be striving for keeping things fair and I've got a lot of practice at catching things and balancing them.

As for characters, I recommend at least one character in the merged magic guild as that's where the most people should be. I will not be accepting characters from other light magic guilds at the very start, but will open up once I have use for them. However, I readily welcome minor or npc characters. You can have as many non-guild shop keepers as you like. And I also encourage villains. Dark Guild baddies are in high demand so I don't have to be all of them :D

I have a friend who is going to be playing a dragon slayer, and I would be willing to accept... I'd say two more at this stage. The cap will likely increase at some point. I don't have so much a hard number as much as I want to make sure they aren't in over abundance compared to the rest of the cast. The same thing goes for S-Ranks. I'll accept a handful but don't want them to be the majority. The Merged Guild Masters will be npcs played by me for now.

And for the last thing about the prequel anime, I wasn't even aware that there was one! I'll have to say that this would be an unrelated story.

Edit : I will not be accepting an S-Rank Dragon Slayer.... unless it's for the Dark Guild ;)