Phonos - Assassin of the Void

Ok I posted this on OCE about a month ago and it got barely any attention so I'm posting it here in hopes that more people will see it and give their opinion.

Phonos - Mage/Assassin

Stats - to be decided

Lore - Somewhat related to kassadin and malzahar as he also walks the void but isn't void born. The rest is to be decided

Visuals - Phonos wears a black leather suit with a hood, a steal plated mask that covers just his nose and mouth and visor goggles. He carries a dagger in his right hand and a long sword on his back (Facing left so he draws it with his left hand). As he moves he leaves brief shadows behind him (Like their radiating off him).

Abilities

Q: Phonos slahes his long sword instantly to a target enemy in X range dealing X magic damage (Numbers to be decided).

W: Phonos blinks to a target dealing X magic damage if it is an enemy (This has a 0.25 cast time), if phonos hits an enemy he may recast it again within 1.5 seconds (Does not count the 0.25 cast time it takes to cast the ability)

E: Phonos throws his dagger in a target direction dealing X magic damage and placing a dark ring around the target, if phonos blinks to the target within 2 seconds he slows them by X% for 3 seconds

R: Passive: Using q behind an enemy champion to exit stealth instead Backstabs them and does double damage.

TOGGLE - X mana per second - After a 1 second delay phonos becomes one with the shadows of the void stealthing himself until he either runs out of mana or uses an ability.(I would imagine to make it fair something such as a lee sin q would also reveal him).