Champion Concept: Phantom, the Nether Blade Assassin

Passive: Nether Blade. Damaging an enemy champion with an auto-attack or ability will be delayed by 1 second. Applying a new source of damage to the target will refresh Nether Blade, stacking all previous damage in a bar visible only to Phantom. If Nether Blade kills the target, Phantom gains 20/30/40% movement speed and 100 energy.

Q: Nether Step. [100 energy] Phantom teleports to a spot within range dealing 30/50/70/90/110 + 5% (+?% AD) of the targets maximum health in an arc and leaving behind a dark cloud that slows for 10/15/20/25/30% and completely blocks vision.

W(toggle #1): Nether Walk. [10 energy/sec] Phantom loses 20/15/10/5/0% movement speed and goes Invisible. W(toggle #2): Nether Rush. [10 energy/sec] Phantom gains 10/15/20/25/30% movement speed. W(toggle #3): Recover. [no cost] Phantom regains 5 energy per second and moves normally.

E: Hidden Blade Strike. [50 energy] Phantom leaps a short distance towards a champion in range and auto attacks, then immediately pulls a second blade and teleports behind the champion, critically striking.

R: Nether Assault. [100 energy] Phantom goes Invisible (disabling his W) for 4 seconds passing through all objects and champions. For each champion hit, Phantom gains 50 energy and deals 100/200/300 +15% (+?% AD) of the targets maximum health.

Notes: The concept is based on the (Japanese?) idea that a character is so fast that an attack's damage happens well after the attack has finished. Since Phantom is the only one who can see the amount of stacked Nether Blade damage, it makes trading in-lane, ganks, and team fighting more chaotic.

Let me know what you guys think.