From Portals of Phereon Wiki

A flexible support skill that can be used on allies or enemies. It's a powerful skill that can stack lots of Burns. It either applies 4 turns of Burns on an enemy, or gives a friendly unit (including self) a status effect that allows them to add 2 turns of Burns with every attack. A must for any fire team wanting to maximize their Burn stacking.

Also see PoisonTongue.