Here's my basic concept for a slayer, and it has a thing that you'd need to okay before I go any more into him. Real basic at the moment, but I think the idea could be interesting.

[hider=CS PROTOTYPE]

[u][h1]Guild Membership Card[/h1]
[/u] Disquised Appearance
[img]http://data.whicdn.com/images/126596540/large.jpg[/img]

True Appearance
[img]https://s-media-cache-ak0.pinimg.com/564x/b0/10/b7/b010b7912067cd976770d3dac0eb6cd4.jpg[/img]

Outfit
[img]https://s-media-cache-ak0.pinimg.com/236x/09/db/e7/09dbe792ed7d0ca05599171d46d388fa.jpg[/img]
[h3]Personality[/h3]
Lazulin is a very sociable young man, despite his rather sullen appearance, always willing to strike up a chat with anyone at any time. He's got a rather inquisitive mind when it comes to machines, and is always eager to take them apart and see what makes them tick and what can be changed to better improve or re-design said machinery to suit his whims. When it comes to the Librarium, however, you'll find very few who hold a deeper hatred of them then he does. In his eyes, they're at fault for what his mother has become, and if he had his way, then the entirety of the Librarium would be brought down screaming. This anger and hatred scare him, as he knows that if he isn't careful, he'll end up just like his mother, but at times it's hard to resist th allure of his darker emotions pushing him to enact his vengeance upon every soldier of the Librarium he comes across.

When it comes to his past before the Cloud Chaser's, you'll find that he turns as cold and aloof as his appearance would initially lead you to believe, never wanting to speak a word of what happened to him to anyone. All anyone knows about him is that he was attacked by the Hellion way back when, and that he was one of the few survives of the event that brought the attention of Pandora upon the demon. When questioned on the similarities between his Slayer magic and that of the Demon's, he simply states something along the lines of how her cursed magic must've somehow bequeathed it to him, as well as giving him his demonic apperance.

[center][i][color=Mediumblue]“So, Librarium thinks it's got what it takes to bring the Cloud chasers down a peg, lads. Let's show them why fuckin' with us is the biggest mistake they could ever make.”[/color][/i][/center]

[indent]|   Nａｍｅ:   |
[indent][i]Mulciber, Lazulin[/i][/indent]
|   Alias|Nickames|Titles:   |
[indent][i]TBD[/i][/indent]
|   G e n d er:   |
[indent][i]Male[/i][/indent]

|   R a n k:   |
[indent][i]A-rank[/i][/indent]
|   Ａｇｅ:   |
[indent][i]19[/i][/indent]
|   Guild :   |
[indent][i]Cloud Chasers[/i][/indent]
|   History:   |
[indent][i]Lazulin's past is something of a mystery as he boarded the Cloud Chaser's ship in the arms of a member who had just escaped hell. An entire Island, populated by villagers and Librarium soldiers alike, had been set alight by blue and black flames that burned both the flesh and the soul. He had been in the Librarium castle, which was at first untouched by the rampage, when the demon had arrived, burning down everyone in her path. . . everyone but a little boy, whom she seemed to be infecting with their dark magic. In a moment of either fool-hardy stupidity or dashing bravery, the cloud chaser distracted the demon for a precious moment and stole the child away, followed by the Hellion's shrieks of rage as she sent out wave after wave of Hellfire after him. However, as he ducked and dodged, one of the attacks happened to hit the boy, and as the child cried out in pain and agony, his arm being reduced to ashes right before his eyes. 

For whatever reason, this caused the Hellion to freeze, and in that moment, allowed for the Cloud Chaser to get away from the scene and from the Island before the entire thing burst into an inferno of profane flames, wiping it clean of all signs and traces of life and leaving naught but a dead rock behind. 

Ever since that day, Lazulin has been riding with the Cloud Chasers, having no where else to turn to. His first few months upon their vessel was spent in sullen silence as he mulled over everything that happened, recovering from his wounds and feeling disturbed by the physical changes that had begun to surface as well. However, after about a year, Lazulin got up, walked to the guildmaster, and asked for something to do. And so he worked his way up from a cabin boy to a prominent member one of the guild's raider teams, always ready to teach the Librarium a thing or two. However, for those who know him well, they get the feeling that he's looking for something or someone, ever vigilant and ever watchful of news that might lead him to his prize.[/i][/indent]

|   Magic:   |
[indent][i]Hellfire Devil Slayer[/i]
Similar to a regular fire slayer, except that he uses the profane energies of the underworld to fuel his magic. Along with burning things and all the other effects that fire has on people, Hellfire can also mark it's victims for a short amount of time. These marks can have some varied effects depending on the spell used, but the most common one is a weakening on resistances and defenses on the target, making them more vulnerable to attacks from him or his foes.

All secondary effects of the Hellfire will be minor to low moderate in terms of effect unless stated otherwise in the spell description(Natsu,if hit by it, could suffer small burns up to the 1st degree(I think that's the lowest) from all sources of fire, for example, though would still be able to safely eat it.)

Illusion Magic: This magic, as the name suggests, allows the user to create illusions to fool the senses of ones opponents, making them believe whatever the user wishes them to believe if they are unable to break free of it or unable to see past the deceptions. At his current level of skill, Lazulin can make rather advanced illusions with an area of about 15 meters, though outside of this area, the illusions become weaker and easier to either break out of or see through. 

A trick he uses to get past his limitations, however, is his prosthetic arm. As a bit of a tinker in his spare time, he's modified the working's of his arm into a magical amplifier by drawing out the magical essence of lacrima, which he harnesses in gaseous state in use to gain a purer form of the Ethernano then what can be gotten from the crystals. By focusing his magic into his arm first, he can increase the range that he can cast an illusion(up to a max of 50 meters), at the cost of both a longer casting time(1-3 posts range, depending on how much he uses) and using up the fuel that makes his arm function. If he uses up all the ethernano gas he has stored within the arm, then it'll be nothing but dead weight until he's able to restore the reserves, a process that takes sometime and focus. He always carries extra canisters on his person, which can also double as powerful explosives when mixed with his Hellfire Magic, though given their importance, this is only used during emergencies.

[hider=Hellfire Slayer Secret Arts]
Hellion's Secret Art: Nightmare: By mixing together his Illusion Magic with the profane energies of his Hellfire magic, Lazulin can cast an illusion spell that can bring about either his or his opponent's greatest nightmare and give it physical form. As such, whatever comes forth from the mind of the selected individual or individuals, it will have a physical presence and be able to hurt them while they're within the area of the spell that is defined by a dome of Hellfire. 

Now while the illusions can hurt those inside, those trapped in the dome can't hurt the illusions, making eiher escaping via barreling out throug the intense and dangerous Hellfire dome, waiting for Lazulin to run out of Ethernano to hold up the illusion, or to find where in the illusionary domain Lazulin is hiding and defeat him. Given the strain this places on his magical reserves, he can only hold it up for 5 posts and during that time, he can't use any of his offensive magics and can barely use his illusion magic to hide himself in the darkened interior of the dome.
[/hider]

 [/indent]
|   Miscs :   |
[indent][i]Has a prosthetic Magi-tech arm that can have it fuel siphoned off to increase the power of both his Illusion and Slayer magic, but this both weakens the power of said arm(which is rather strong when it holds three full charges of pressurized Ethernano gas, and can even be over-charged itself by using one of charges to unleash either a super-punch or a short burst of super-strength), meaning he has to choose when and were he uses these charges, when he has time to refuel(carries about 6 canisters on his person if given time to prep), and try to not get said canisters hit in the middle of a fight.
[img]http://img01.deviantart.net/473e/i/2014/320/b/e/steampunk_mechanical_arm_by_skinz_n_hydez-d86o89c.jpg[/img][/i]
[/indent] Note: Ethernano gas, while more potent than regular lacrima, is also highly unstable. While !making specialized weapons out of it is do-able, it requires too much maintenance to be used on a large scale. It also means that those who make use of it habve to be careful not to get themselves blown up in a fight while carrying it on their person. Also, unlike Lacrima, it can be used up much more easily, making it better for things like guns and such, but not things that require a lot of use(his arm being an exception)

[url=http://orig06.deviantart.net/5e19/f/2013/183/4/1/629_manga_classic_revolver_by_blackdonner-d6bqq7l.jpg]Ripper[/url] is the name of his self-made Chain-cutlass, powered by a normal lacrima crystals, that can tear through most metals when it's turning at full speed, and can be further enhanced by adding Hellfire to the mix, though this can only be done fro brief swipes, as too much will cause the delicate parts in side the machine to melt, rendering it unusuable.

[url=http://nerdapproved.com/wp-content/uploads/2012/09/cutlass.jpeg?x35072]Black Delilah[/url] is a revolver that can be enhanced with Pressurized Ethernano Gas, put dosn't require it to function, instead only needing a small amount of the user's ethernano to fire off it's ammunition.[/indent][/hider]