Thnderlords decree

Check the history of the game where it failed, I have a theory that it bugs out if two people on the same the same have it.

Yup. I've used Kayle frequently and most games it will proc, but there have been a couple games where it literally never procs once. One recently I remember was me against a Syndra.

Yes, first game as Xerath against a Zed, stunned him, W-Q instacombo followed, no additional damage dealt... #lovenewmasteries