[Champion Concept] [Xiodias, the Lights shadow]
Lore: [-Ze-Oh-Die-Ass-] Deep in the Shadow Isle's twisted caverns, Xiodias lay. He found toying with Light fascinating. Often the Light would try to escape. However Xiodias was too fast for the Light - as he would catch it. One time, Light had almost escaped his caverns, it had all its other friends with it navigating desperately. But the cavern proved too much for the Light, thus it remained shrouded. It remained to Xiodias.
Not many know what horrid things Xiodias did to the sailors. He -... She-... It would simply drag the sailors, one by one into the caverns. Many stay away, as they know their light, is being shadowed.
Primary Role: Assassin Secondary Role: Fighter
Abilities:
Passive: The Lights shadow When the enemy team lose sight of Xiodias for 3 seconds, his passive will trigger.
The next attack or damaging ability will do 3% (+2% per level) extra damage (much like Kha'Zix)
Q: Thirst for death Xiodias' thirst for death allows his next attack to place a death mark on the target, which will deal 60 (+40 per level)(+100% AD) over 3 seconds.
Shrouded Mist effect: The next 3 attacks apply an AOE effect version of the original.
W: Passive: Dark passage Xiodias gains 2% (+2% per level)(+1% of bonus movement speed) extra movement speed when unseen by the enemy. This buff is disabled in combat.
Active: Shattered Rays On the points of a pentagon, 5 ray's of light appear around Xiodias. Enemies that walk through the rays gain +10% movement speed, which decays over 2 seconds - to then be slowed afterwards for 10%/15%/20%/25%/30% and damaging them for the movement speed gained as magic damage +80% AP
Shrouded Mist effect: Instead of 5, there are 9 points in a much larger area (375 -> 600) and the effect is doubled.
E: Ruin Xiodias dashes to an enemy, slowing them by 30/34/38/42/46% for the next 1/1.25/1.5/1.75/2 seconds.
Shrouded Mist effect: Stuns for 0.5/0.75/1/1.25/2 seconds if the enemy if dashed to inside the Shrouded Mist, slow still applies normally.
R: Shrouded Mist Xiodias creates an area covered in a Mist of darkness. Whilst inside the mist, Xiodias gains: • 20% (+5% per level) attack speed • 5% (+5 % per level) attack damage • More powerful version of current abilities / Abilities are enhanced Enemies are slowed by 1% (+1% per second)(Max slow from R = 50%)
Recommended Items:
For Jungler:
For Laner:

Other details:
Inspirations by:

I made this purely out of fun, it would be EPIC to see Xiodias in LoL, especially as he is kind of OP. ( I think at least) I am happy to listen to feed back and what you would change (Which isn't the whole champion) from Xiodias kit. Feel free to add me on EUW, summoner name is MildMild.
BUFFS / DEBUFFS:
Q:
Xiodias' Q was decent, but he needed more hard CC while in his Shrouded Mist.
**+ on the 3rd attack, all enemies or monsters caught inside the AoE effect are stunned for 0.2/0.4/0.6/0.8/1 seconds.
R:
His ultimate seemed weak most of the game neither did it scale well into the late game, however the attack damage is a potent buff.
+50/100/150 Attack range 5%/10%/15% attack speed -> 10%/20%/30% attack speed