This is the first time I propose a champ.. please go easy on me :)
First off, a bit lore... Crystal is a guy (just cause a butterfly mage being a female is kinda cliche and also I have a Semei (japanese omnyoji) kinda image in my head). Crystal was born with rainbow coloured eyes but strangely enough he couldnt see any colours (he was born totally colourblind). Since he was colourblind he had no apreciation for beautiful colours but he always liked butterflies due to the many beautiful shapes that have on t heir wings. One day he notices a buterfly that was caught in a spiders web, as he see the butterfly strugling to free herself he decides to help her. As he frees the butterfly to his surprise the butterfly thanks him in a weird language that he (to his second surprise) understands. The butterfly was mesmerised by the colour of his eyes and when he explains to her that he is colour blind the butterfly will help him in return. She guides him to the land of fae (Yeah I know similar to Lulu..) and takes him to a shrine where an artifact holy to the... butterflies is held. The artifact is the twin fans! One blue fan that feels cool to the touch and a red one that emmits a heat. Well Crystal takes the fans and he becomes the Butterfly avatar (and yes his colourblindness was cured).
Sol lets get to abilities.. Well his playstyle is changing from melee to ranged and he is a mage. Writing details about health and mana amount is something that i m not good at.. ( I apologize).
Changing from melee to ranged: Crystals Q and E each transform his fan into butterflies, the butterflies attach themselves to enemies as long as the enemy is within range and for a certain period of time. While even if one oh his fans is attached to an enemy Crystal has ranged attacks. Only one butterfly can be attached to an enemy. If a second butterfly is cast on the same target the first one will return to Crystal, but both skills can be cast at the same time on 2 targets (one with Q and another with W.
When Crystal is melee: every time he kills a minion he restores a flat amount of mana.
when crystal is ranged: everytime he kills a minion he gains attack speed buff for 3secs (9 secs cooldown)
Q: Red butterfly. A point and click ability. Crystal summons the fire butterfly spirit from his left fan and the butterfly attaches themself to an enemy revealing them doing magic dmg and applying a burn for a few secs, each time Crystal auto attacks the enemy with the red butterfly the burn effect is renewed.
Q recast: Crystal can recall the red butterfly early, when the butterfly returns it restores a portion of his health depending on the dmg it caused (including the renewed burn dmg)
W: Blue butterfly. This is a skillshot. Crystal summons the water butterfly spirit from his right fan and shoots her in a straight line dealing magic dmg to enemies and slowing them down. The butterfly goes through minions but if it hits an enemy champion it attaches themself to them. Crystal's auto attacks create stacks on the enemy champion with the blue butterfly. The stacks decay with time, but the time is renewed every time Crystal auto attacks. If 3 stacks are reached the champion is rooted.
W recast: Crystal can recall the blue butterfly early for a movement speed buff.
E: Butterfly dance: Melee form: Crystal dashes towards a direction and spins with his fans at the end of it dealing physical dmg
Ranged form: Crystal dashes towards one of his fans retrieving it and reapplying the fan's effect.
R: Swarm: Crystal summons swarms of butterflies around him, getting huge cooldown reduction on his q and w and increased range he can keep casting them summoning new butterflies (so he is able to attach butterflies to the whole enemy team, but only one butterfly in each champ). During swarm Crystal is unable to move or use auto attacks. At the end of the spell all the butterflies explode, blue butterflies root the enemies and red ones deal extra max health percentage dmg.
Role: Primary role midlane, secondary role support (?)
Gameplay: For the most part u need to hit with ur spells the enemy champ so u can use ranged attacks to farm and poke. Using ur spells to keep poking the enemy and keeping ur health high withthe red butterfly and when u are low in mana u change to melee to make use of ur passive and restore mana. Timing ur W with last hitting a minion gives u an attack speed boost to help u stack the root.
Build: This champ is very versatile with ways u can build him. You can build attack speed to proc the effects of Q and W. Or u can build flat ap and movement speed. Or even u can choose an ad build. :)