Torus, the chain wielder.

He should be a melee, support based champion using chains in all parts of his concept in both close ranged autoattacks and ranged "tether" abilities.

Innate: (Breaking links)

If hit by an ability from Torus the target will be left with chains attached and will be slowed by 2,4,6,8,10,12,15% for 1.5 seconds (progressive in leveling, lv1, lv3, lv5, lv7, lv9, lv11, lv13) This will not stack with itself.

Q ability: (Branching chain)

A tether (range 600) similiar to leblanc's etherial chains but snares instantly for 1 second, deals physical damage and then, after released from the snare, slows by a further 2,4,6,8,10% (on top of the passive slow) Skillshot based with a low-medium cooldown.

W ability: (Whip leash)

2 chains fly out and latch onto the lowest % health enemy champion (600 range) to pull Torus towards them dealing moderate physical damage and applying the passive slow.

E ability: (Wrapping-up)

Torus attaches chains to his hands and links his chains together around him, granting extra physical damage and armor, however this will slow Torus by 14,13,12,11,10% while the chained effect is active due to their weight. (This can be toggled with an initial cooldown of 12 seconds at all levels) (Additional 2,3,4,5,6% attack damage and 10/20/30/40/50 armor)

Ultimate: (Launch and ground)

Torus lauches heavy chains at the closest 2 enemy champions (non-skillshot), snaring them for 3 seconds and dealing large physical damage. After the snare, the passive slow is doubled and extended to 4 seconds. (This will take priority over any additional slow applied by Torus)

Just an idea but there are no full chain based champs and i think this one can be built to use either mana or energy (will restore energy if the Q ability hits) like the other ninja champs energy return. Items like frozen mallet will not stack with his passive for his abilities but will apply on auto attacks until an ability is used.

Hope you liked the idea, i am unsure if it would work in the real game but it can't hurt to write this here and see.