In the other thread Shuhei and others have made some good arguments for Curses
Instead focus your efforts on producing Demons and Curses! It's the only new thing to pop in to the FT universe for a while and the only thing we made no effort to introduce on the site. To counter-balance the Demons & Curses maybe add Angels and Blessings lol. -Shuhei
What I'm more interested in is the Curses deal. I made a "Curse" a while back with Hydra, but it was just magic with a fancy name. I'm really interested in how you think this would change things though, as I've been curious about curses since the idea came out (while I was making my demon character). Can this honestly become a discussion at some point? -Axil
But more importantly, the bigger issue. There are way too many slayer types... I agree to bring in the curses and demons!! Yaya! -Lyra
So let's talk ideas
Demons:
I feel demons should be opened as a playable species. Demons will be unable to use magic however will be able to acquire an infinite amount of curses. They also take extra damage from demon slayer magic.
BUT WAIT KIRAFACE! Infinite curses is too op for this life! Well I do believe I said "acquire" Which brings me to the next topic
Curses:
For the sake of equality I think we can bend the rules presented by the manga and say ANYONE can get a curse. But there are rules to be considered, rules of usage and rules of obtainment.
Curses can be obtained in place of secondary magic for humans while Demons are allowed to start with it as a primary. To obtain a curse a Book of Zeref must be found(with exception of the one curse a demon starts with). Books of Zeref can be bought, obtained in events or obtained in special jobs as rewards. Each Book of Zeref has a pre-written curse created by the development team not to crush creativity but to ensure that the Curses follow the strict "usage rules." As stated in the demon section assuming a demon keeps finding books they can keep getting curses as long as the demon keeps all the books recorded in a thread in their character vault. Having staff pre-make the curses will also make it hard for a demon to get a couple books that combine into an invincible power.
Now onto usage. Based on information gathered from Jackal talking about his curse I designed an idea for curse function. A curse sets a condition on the player. This condition does not use up Mp or have a duration, it just always is. For example Jackal turns anything he touches into a bomb, based on his description it would seem he does not have control of this effect. The strength of a curse over magic is that unlike magic it never runs out, the draw back is that the user cannot stop using it if they so desire. An example(silly example) of a curse might be "Everytime the user greets someone that person is struck with lightning" a very useful power in combat but it has obvious drawbacks in that the person holding it will smite their friends every time they say hi. A curse is meant to be something bad, having a curse is a bad thing, but a resourceful person can turn it into a weapon.
Other examples:
"Everything the user bites will suffer spontantious combustion." Pro: Explosive bite attacks Con: Only able to eat burnt food
"Everything the user steps on freezes" Pro: Awesome kicks Con: Don't walk on the grass
"Laser eyes" Pro: Laser eyes Con: You can't turn them off
Curses naturally should be this simple because of how simple they are in the manga. Also if development has to pre-make a ton of these if they have one sentence descriptions it won't be so hard for them. More complex curses like Soul Dude or Mard Geer's can be made available as items of the month or through events. However they would follow the same rules, just maybe two or three sentances.
I believe this method I have described best mimics canon curse mechanics.
Note: A demon's first curse can be made themselves but requires TWO mods to approve.
People have mentioned Angels but meh