I had an idea for a League of Legends champion whilst working in the bakery at Safeway. It struck me that there were very few musically inclined champions in League of Legends, and my mind thought of a pair of champions who could fix this.
So, I introduce Lilly and Silas - The Controversial Couple!
I shall start with Lore, for the sake of setting the scene.
Lilly was once the leader of a coven of sweet-talking harlots, often swindling weaker men to do her bidding, and then ripping them of their money. She often times murdered them in their sleep and had her underlings get rid of the corpse. The Noxian High Command had felt wind of her deeds, and in order to get rid of her as a problem, forced her into military service as an apprentice under Katarina. Preferring to flirt, murder, and then ask questions later, her training was bitter and not very exciting as she loved to see the emotions of her victims pour out in their final moments.
After eight years of decidedly boring training under Katarina, she was finally given leave to work on her own. It was during this time she met Silas - or rather - attempted to murder him. She was assigned to eliminate a Demacian Noble, specifically, Silas of House Spiritmight. She watched him for months, following her training, but could not find a way to dispatch him without blowing her cover and failing the mission. Then, her past kicked in. Lilly began her old ways of flirtations with Silas, and this caught his eye immediately.
Silas knew she was not from Demacia - he could tell by her demeanor and the look in her eyes. This did not stop him from taking an interest in him though, because he quickly found himself in love with the unpredictable Lilly. His next actions proved to be beneficial to himself, as well as Lilly. He showed her compassion and caring - something she had never seen in the cruel reaches of Noxian borders. This stirred something deep down inside her, and caused her great pain and anguish. For the first time in her life, she did not want to kill a man, though she knew she must to please her Noxian overlords.
Silas kept opening doors in her heart, prodding with questions to learn more about her. Eventually, she broke down, slipped to her knees and burst into tears inside his home, explaining everything - including her mission. Silas, strong, yet tenderhearted, found true love inside her - something he had thought not possible from any Noxian scum. Instead of reporting her, or outright slaying her, Silas came to her level, wrapped his arms around her, and said, "That doesn't matter, because I love you." Lilly and Silas embraced the new-found love, and realized that their rivals are not as bad as they have been lead to believe.
Lilly and Silas have been together ever since, and have found through their adventures together their many inherent talents - Including Silas' passion for dancing, and Lilly's love of murder. Paired together, there is no finer way to die, than to die dancing your life away.
Skills:
Hidden: Whenever music is played near Lilly or Silas, they gain +1 attack damage, +1 armor, +1 magic resistance, and +1% movement speed.
Passive: Dancer's Dexterity: Every time Lilly and Silas use Shuffle, they gain +10% attack speed and +25% movement speed for 5 seconds.
Q: Shuffle:
Cooldown: 30/25/20/15/15
Switches movement control between Lilly and Silas, as well as which character casts spells. This spell also activates Lilly and Silas' passive. (Lilly and Silas can cast the same 3 spells, as well as shuffle. Which character casts the spell is dependent on which character is being controlled. Think of Shaco's clone, but with the ability to cast spells.)
W: Slide
Cooldown: 35
Mana cost: 40/55/65/80/100
Range: 525
Currently controlled character slides across the ground becoming untargetable during the duration of the slide. On collision with another unit, causes 50/100/150/200/250 (+ 75% attack damage + 25% ability power when cast as Lilly, +25% attack damage, + 75% ability power as Silas), knocking up and stunning the first unit it passes through, then slowing all others.
E: Charade
Cooldown: 25/23/21/19/16
Mana cost: 50
As Lilly, a dagger is thrown at target, dealing 75/100/125/150/175% attack damage and slowing their movement speed by 20% for 2/3/4/4/5 seconds.
As Silas, the target is charmed for 2/3/3/3/4 seconds and walks towards Silas. If the target attacks Silas within 2.5 seconds after the charm, the target takes 50/75/100/125/150% of ability power in magic damage.
R: Dance of Death
Cooldown: 100/80/60
Mana cost: 125
Range: 700
On cast, a band appears from the ground around Silas or Lilly to play music (Hence the reason for the gold cost.) All characters within 700 range must dance(same as /dance) for 2/3.5/5 seconds. This includes friendly and enemy players. Dancing Champions are unable to take any action (skill, movement, item, attack, summoner spells, and b, though they can chat) until the time is up. If Lilly or Silas are killed during this time, the dancing, and music, stops. This skill activates Lilly and Silas' passive.
Hidden passive: If Sona or any Pentakill-skinned champions are within range, they play music.
Lilly and Silas have 800 range before they must return, much like Shaco's close, or Annie's Tibburs. This allows Silas(or Lilly) to use the ultimate, and then still autoattack as Lilly (or Silas).
Starting stats:
Health: 440
Health Regen: +0.6
Mana: 200
Mana Regen: +0.6
Attack Range: 125
Attack damage: 52 (+2.6 per level)
Attack Speed: .5 (because there are two characters who can attack at the same time)
Armor: 13
Magic resistance: 30
Movement speed: 360
Now, for character design, I suck. Seriously, bad. I cannot draw, and am in no way artistic.
Lilly is Noxian, and dresses that way. Silas is Demacian, and dresses in that way. White and Black color scheme would be appropriate for a default skin.
Let me know what you think, because I'd like to see my idea on the scoreboards one day.
If you have any questions on the mechanics, feel free to ask. 
-Psychrom