The light comming from the little fireflies surrounding this special rune attracts enemies easily, luring them towards it's wielder and away from the others. Attached to someones skin, make sure the person has some worth seeing defense and hit points - he'll become your tank of the party. Equipped properly a damage absorbing target can protect your casters and weak characters.
Pushed into the battle by his mother, the spear-fighter Eugene is always bound to the Firefly Rune. But it can be found in other areas of the world also, letting you decide whether to concentrate your physical defense to one special member or not. Keep in mind the runes effect works for attacks targetting a single antagonist only and not for magic either. It is very well possible to build whole strategies on this rune, especially for Suikoden Tactics.
This is a child of the Great Firefly Rune which attracts whole enemy parties throughout your travels. - Celes