It's always nice to become berserk, isn't it? Well, at least for some of the hot-blooded folk. The rune takes effect either when damage equal to half of your maximum health is receive or after beeing hit twice, which depends on the game you found this little crystal in. And while berserk you'll go definitely on a rampage with tripple the attack power as before. Ouch!
The Violence Rune can be used to inflict damage far beyond your imaginations and it was during some tests in Suikoden II already to break the damage limit with Valeria and her Falcon Rune. Sometimes it is well hidden, in case of Suikoden II in a bookshelf in Rockaxe - and sometimes it is not and is simply sold in shops, in case of Razril in Suikoden IV. - Celes