New status effect idea

Oblivious

A champion affected by this kind of crowd control has their passive buffs temporarily deactivated, cannot use item actives and lose half of the stats granted to them by their current items... or something along these lines...

The point of this form of CC is to give players the ability to actually respond to certain things that are just menacing in all regards ... and since most hard CC only last basically long enough for you to blink your eyes and its over (a bit exaggerated but you get my point) it doesn't break the game... this one would fall somewhere in between hard cc durations and soft cc durations.

So, an example. While affected by this CC, for that instance, Vayne does not get 30 movement speed and her BAs do not apply silver bolts. Tahm Kench would lose his ability to apply stacks of an acquired taste and his bonus damage based on his health, and so forth... passives like Pantheon's blocking ability, which have an active state (when he will block your next appropriate attack) and a passive state (when he has to do whatever he has to do to activate that blocking state), while active... become inactive and during the duration, he cant just reactivate it, but immadiately after the duration of the CC, he gets his blocking state right back if he had it on prior.

Essentially, it's a form of CC that would be as valuable as stunning an enemy and in fact, unlike alot of OTHER CCs, RETAINS it's value even while the target is stunned... Because if you stun someone who was just feared... they're not gonna stack, they'll both wear off. But this one, if you Obliviate (not even sure if thats a word) someone whos stunned, they would take a drop in their defenses because even the stats gained from their items is reduced...

EDIT1: This is a STATUS EFFECT... not a spell, character ability, none of that, and just like slows it can be magnified as seen fit depending on how you're acquiring it... if it's a dirt cheap acquisition then the debuff granted by this status effect (far as the item stat gains go) would be like... 10%... not much... but if it manages to find it's way onto an ult that has a 5 minute cooldown and it's the most telegraphed skill shot possible (topping even Xerath's ult) then by all means, a 90% reduction would be nice... because players should be rewarded for doing the near impossible.

In all cases though, passives (champ and items) would be deactivated and item actives as well for the same amount of time- and this time frame isn't something ridiculous.. it's just... likely 1 second, 2 seconds for some costly uncommon method to use it.

Comparing it to an already existing game making CC. Stun. It'd fair as the following

Stun: Stops everything (movement, attacking, abilities) but can be reduced and you get to keep flash and teleport (teleport would be stopped if you're stunned mid cast)

Oblivious: Stops all passives and item actives, but you can still move, attack and cast active abilities and all your summoner spells and it wouldn't interrupt anything that's happening due to an active (it would freeze things that are happening due to a passive however) however it CAN'T be reduced and it stops reduction on OTHER CCs while in effect

Items and champions created to be able to utilize this effect would have to have glaring weaknesses ofcourse.