Ok so I think Teemo's poison should do this, its his ability that is causing the damage and in the description says it is activated by the 3rd attack or damaging ability, however, I agree that's its pretty op. I noticed in the last patch that it was "fixed" on Teemo and it no longer does this because it was not intended. So If Teemo's ability's are not allowed to trigger the effect then why are all the other poison based toon's allowed the effect. (ex. Morgana, Twitch, Singed, Gangplank ect.). I know for certain that Morg's pool does it and fairly certain of the others (not tested however because I use other keystones on these toon's).