The Berserker is strong defensively, and it can summon a Centaurion Blade to attack alongside it. The blade will disappear if the Berserker is killed.
It is better to approach the Berserker with a preemptive strike to stagger it before it uses Forge Blade. If a preemptive strike is not possible, it is best to start with a COM/SYN/SAB or MED/SYN/SAB paradigm, buff up and use Deprotect and Deshell to stagger it as fast as possible, launch it up in the air and keep it up before it can use Forge Blade. If it does use Forge Blade, the Centaurion Blade should be the party's main priority as it can deal heavy damage. However, the blade will disappear if the Berserker is killed first, so it is best to go for the kill if the Berserker has low HP.
Berserker was originally a term for Norse warriors who fought with uncontrollable rage and reckless disregard for their own lives. The term itself is typically translated as "bear's skin" in reference to the animal skins Vikings would wear into battle. Theories about what causes berserkergang, the fury Berserkers go into, include possession by an animal spirit, drunken rage, and ritualistic dancing. Berserkers are often depicted in art as men with crazed eyes biting their shields in anticipation of battle.