Rage is a state where attack and defense stats are temporarily increased. Rage builds are common for players with high defense. Rage does not increase dodge rates.
Rage triggers automatically when an orange bar below the player's health reaches maximum. When this happens the player will glow orange for the duration of the rage.
The duration of Rage is usually very short, however it can be increased by the "Burning Warth" ability.
The amount of attack/deffense increase is 20% of the base status, however if you are a Spearman it can be increased by the "Reigns of the VIolent Gale" ability.