League of Legends XL: Season on Hold 'til Morello gets Gold

[Psyborg]

I considered the effect based on missing resources, but it has a number of issues:
1) Your idea for CD-only champs works, but is really clunky, difficult to wrap your head around, and obviously forced
2) What about champs like Rengar? He could easily have zero fury when this goes off, and it feels bad that he's randomly either punished really hard or not at all based on where in his fury rotation he is
3) It actually hurts mana champs the least by far. Energy champs are designed to blow all their resource, then have it back soon, so they'll probably have very low resources when it goes off. CD champs also front-load all their abilities and put them on CD. But mana champs? Late game, they often have huge mana pools that they don't have to worry about; they could easily be at half or 3/4 mana at the END of a fight, let alone towards the beginning of a fight when you probably want to use this (especially to take advantage of the silence)...

I'll let you know if I come up with an ultimate I think fits with the theme.

Suggestion A: Deals (X damage + Y ratio) damage, increased by (Z%) for each enemy ability that's on cooldown, and silences for (t) seconds.
Suggestion B: Deals (X damage + Y ratio) damage, increased by (Z%) for each ability the target has used in the last (N) seconds, and silences for (t) seconds.
Suggestion C: Deals (X damage + Y ratio) damage, and silences for 1 second + 0.75 seconds per ability used in the last (N) seconds, [optional:] to a maximum of (Q) seconds.
Suggestion D: Deals (X damage + Y ratio) damage, and silences for (t) seconds. This ability's cooldown is reduced by (Z%) of the base cooldown amount for each ability the target has used in the last (N) seconds.
Suggestion E: Deals (X damage + Y ratio) damage. Any of the target's abilities that are currently on cooldown have their cooldown remaining increased by (t) seconds.

In any case, champions with multiple passives and/or toggles will be less vulnerable, and Karthus/Cass/Ryze/Lee are kinda boned, but whatever.