It caused a monster currently engaged in combat to retreat. This effect was commonly exploited to steal monsters from players training melee, allowing the player who casts the spell to receive all of the experience and loot from a monster with already decreased Hits.
↑Kamykazee. Forever Runescape: Part 1. Rune Tips. "This was a widely used kill-stealing technique. It was cast on an NPC someone was fighting causing it to flee so that the person who casted the spell would finish off the kill and receive all the experience and spoils." 29 May 2011.