It's real simple, and probably likely to be attached to another ability, but consider the following. An ability, or mechanic attached to an ability, that makes every enemy on the other team hear a Fiddlesticks VO line. A creepy laugh, a menacing line, a hoarse "Comin' for dat booty". Something to that degree.
Maybe attach it to his Fear ability (if he keeps a Fear), but only if he doesn't hit a target with it, everyone suddenly hears Fiddlesticks.