First time doing this so im going to keep it short and sweet. Feedback welcome!

Name: Rith - The Shadow of War
(Passive) - Darkness : In a small circle around Rith shadows are always trying to free themselves from his grip reaching out of him, grasping, clawing and biting anything they can. Enemies that come to close to Rith are Inflicted with Darkness a DOT with damage based on enemies current HP. The DOT deals 4 / 7 / 10% of HP in magic damage over the course of 5 seconds.

(Q) - Puppet of Shadows : Skill Shot : Ignores minions : Rith releases a shadow that creeps along the ground, if it hits target champ, the champion mimics Riths movements for 1 / 1.5 / 2 / 2.5 / 3 Seconds (Enemy player loses control for the duration)

(W) - Children of the Shadow : AOE around Rith : Riths shadows start to leak out of him in an AOE circle around Rith, anyone within range is pulled slowly towards Rith for 2 / 2.5 / 3 / 3.5 / 4 Seconds. (This ability is best used after you land Puppet of Shadows)

**Scenario : You land Puppet of Shadows making enemy mimic your movements, so you run towards the enemy causing them to run towards you, popping your W the Enemy is now slowly being pulled with you for the duration**

(E) - Bane : Surrounds target teammate in shadows, dealing 5 / 10 / 15 / 20 / 25% of their HP in damage to them instantly. Granting them a bubble for the amount of damage Bane inflicted as well as 10 / 15 / 20 / 25 / 30% life steal for 5 / 5 / 10 / 10 / 15 seconds.

(R) - Deaths Embrace - Shadows shoot out from Rith like tentacles grabbing up to 5 near by enemies within range, if anyone is caught, they are slowly pulled towards Rith for 2 / 4 / 6 seconds and take 10 / 15 / 20% of their current hp as magic damage.

** think of it looking like Morganas ult but instead of being stunned and being able to walk around freely they are tethered and being pulled slowly into Riths passive range.

Passive: 10% sounds like a lot for a passive. make it 5% at lvl 18, maybe.
Q: 3 SECONDS? that is way too long. make it, at max, 1.5
W: where is his damage? 4 seconds is also very long
E: What? why deal a fourth of their health in damage to allied champions? the life steal does not make up for it. not to mention this ability WILL be used for griefing.
R: enemies? or enemy champions? 6 SECONDS? dude, be realistic.

Overall: too many things are overpowered. Understand that I like his concept, but your execution of his kit is bad. He has no damage that scales off of anything but their hp, this makes last hitting minions with spells near impossible.
If anything this champion can be a support with little damage like zilean, but he has too much crowd control and his damage is not very helpful.