So, I was wondering if Blade of the Ruined King and Frozen Mallet would proc on Judgement hits? It seems Frozen Mallet does, but I'm 100% sure. I don't know how to test it for Blade of the Ruined King. Because that would make garen very strong, if it was the case (I mean, even stronger)
If you want to test for yourself, play a custom game where you lane against a Sion, let him stack tons of health, grab a BotRK and use Judgment on him: if it does interact with Judgment, it should shred his health even if he's at ridiculous values, and if it doesn't, you shouldn't be dealing much damage against him (assuming he also isn't marked as the Villain).
@Willbachbakal, thank you. That's reasonable. Garen would be absolutely the most broken champion in LoL history if Judgement did proc BotRK. I don't know what I was thinking. It does seem to apply Frozen Mallet's slow and The Black Cleaver's armor penetration stacks. What's up with that?
If it's applying FM's slow then that's a bug, as it's an on-hit effect and should not be applied. The Black Cleaver's armor reduction, however, applies on all applications of physical damage, which includes both basic attacks and physical damage abilities, so having it apply on Judgment is normal.