Champ Concept: Nobuo - The Lone Swordsman

This is the first champion concept I came up with,so please tell me what I can improve :)

Info: Name - Nobuo Gender - Male Race - Human Birthplace - Unknown (Possibly Noxus or Ionia) Faction - Order of the Shadows Occupation - Keeper of the Shadow Box

Some lore :

Once,Nobuo and his Brother Zed lived by themselves wherever they could.Zed was a powerful warrior,but Nobuo was way stronger,Nobuo used a sword technique called The Blood Baptism ,which costed him a tiny bit of his lifespawn when he was using that technique.However,one day,Shen and his father found the two boys playing around his temple,so he tried to make them go away.Nobuo didn't want any trouble,so he told Zed to go away,but he didn't listen.Zed was then knocked out by one punch from the master,and he got taken inside the temple.When he saw that,Nobuo didn't know what to do,so he ran away.He then walked all around the rift to find a way to become the strongest swordsman around Runeterra,so he can protect his friends and family.He went in Noxus,where he got sent out-he went in Demacia,where he got exiled.He went even in the Howling Abyss,but there was nothing but death. Then,after 5 years of walking and looking for something to help him,he gave up.He went back to the temple to take his brother back.When he got there,the only thing he saw,was the master dead,and then the young man called Shen and his brother,Zed fighting.Zed had an evil look in his eyes,he had to stop him.Then he quickly drew his sword out,created a blood wall so his brother Zed couldn't escape,and then he shouted 'ZED!' Zed was filled by the Shadow power,so he didn't recognise him.Zed quickly used his shadows and got in front of Nobuo,trying to kill him.Nobuo didn't want to do this,but he had to.He drew the shadow power from Zed,destroying the living shadow.However,Zed's powers weren't completely gone,he was still able to use his shadows,but not as strong. However,the shadows quickly started going through Nobuo,trying to take over,but they failed.So now,he has the power of shadows.He then took Zed,and vanished,into the night...

SKILLS: (this champion doesn't use mana,energy or blood.he uses lifespawn energy.) Lifetime energy is like blood,but if you get that to 0,your max hp will drop to 15% + 10% of bonus hp (level 1-6) 25% + 10% of bonus hp(7-11) and 40%+20% of bonus hp.Your lifetime energy is 50% of your current hp + 50% of your current AD and AP Passive : Death Scratch Nobuo's next basic attack will strike 2/4/5 times,applying a stack of Corrupted Blood for each basic attack.Each bonus attack deals 5% more damage,meaning at level 16 you'll deal 25% bonus damage on your fifth attack.Cooldown : 25s/20s/15s Q-Shadow steal/Blood loss Non-toogled - Shadow steal : Nobuo's every 5th basic attack on the same target steals their shadow,slowing them for 25/30/40/45/50% for 1/1.5/2 seconds,and increases your damage by 5/10/15% of your target's bonus AD Toogled - Blood loss : Nobuo loses 5/10/15 hp every single auto attack on the same target,but he deal bonus magic damage over time scaling 5/10/15% of your AD W-Pure death Cost:10% of your lifespawn energy Nobuo kills any friendly target(minions and Champions )healing him for 40/50/65% of target's current hp.This is halved for champions.If spell is casted on an ally,it doesn't kill it,but that champion loses 10/15/25% of it's current health.The champion must be out of combat and have more than 40% hp. Cooldown: 20/17/15 seconds E-Shadow path Cost:20% of your lifespawn energy Nobuo baptises the area around him for 1 minute,granting him 10/13/15% increased damage and healing,and also whenever he doesnt attack or gets attacked for 5 seconds he gets a shield for 10% of his lifespawn energy Cooldown: 75 seconds R- Mark of the Secret Technique Cost: 0 This skill can only be used on champions without a shadow Nobuo become invincible for up to 10 seconds,and he strikes EVERY single champion that he had the shadow of,dealing 50% of his current lifespawn energy,+ 10/14.17% of the damage the champion has recieved in the last 5 seconds Cooldown:120/100/90 seconds

I think this champion would be a bit OP,but It'd be fun to dash to every enemy around the map and attack them for 1000 dmg ^>^ Please comment what you liked and what you didn't like and how I can improve it,ty ^>^