Abilities that slow interaction with oppressor

Solution 1:

When an ability hits an enemy, the game calculates the result. In this case, it would calculate the Champion's new movementspeed, and the Champion's new Current Health.

This means that they are applied at the same time, and as such it will not make opressor trigger with the same skill. In other words, the target needs to be under Crowd Control before the Opressor triggers, even if the ability you use has CC in it.

Solution 2:

In my personal experiences, i believe the damage is applied first, since the slow effect is only applied IF it hits the enemy, therefore it will first apply the damage, then the slow, meaning opressor will only help you deal more damage on the next hits.

I will test it later this evening to be sure, but for now this is how i believe it works.