I know there are many ideas being thrown around but i think this one could work.
I haven't thought of a name just a concept but i think he/she should be a melee, tank based around the use of chains, in both close ranged autoattacks and ranged "tether" abilities.
Passive, If hit by an ability from this champion the target is slowed by 3,6,9,12,15,18,20% for 2 seconds (progressive in levelling, lv1, lv3, lv5, lv7, lv10, lv13, lv16) This will not stack with multiple abilities.
Ability 1, A tether 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 3,6,9,12,15% (on top of the passive slow and this would be a skillshot).
Ability 2, A chain is thrown at an enemy dealing physical damage and slowing by 20%, slow is applied from passive as normal (Not a skillshot)
Ability 3, The champion attaches chains to his/her hands granting large extra physical damage, however, will slow the champion by 20,18,16,14,12% while the chained hands are active due to their weight. (This can be toggled with an initial cooldown of 15 seconds at all levels)
Ultimate, The champion lauches heavy chains at the closest 2 enemy champions, snaring them for 3 seconds and dealing large physical damage. After the snare, the passive slow is doubled and extended to 5 seconds. (This will overide the passive slow from other abilities used and will always last the full duration but still will not stack with other abilities used after).
Just an idea but there are no chain based champs and i think this one can be built to use either mana or energy (will restore energy if ability 1 hits) like the other ninja champs. Items like frozen mallet will only give the 15% slow for his/her abilities, even those that are single target abailities, due to the passive.
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.