Eorzea is mine by right!
Gaius van Baelsar is fought as the first stage of the final boss sequence in Final Fantasy XIV.
This fight is relatively simple but be prepared for a lot of running because Gaius will teleport around the area fairly often.
Gaius's basic attacks won't hit too hard in the early going, as he goes easy on the party and will use Innocence, which strikes as a cleave for roughly 800 damage on a tank. After taking off about 5% of his Gaius will move the fight to the next phase.
The next phase starts with Gaius applying a bleed effect using an unnamed ability, dropping an AoE zone of blue fire and use Sentence to lunge after random players dealing moderate damage and heavy Knockback. He will also fire random shots at the party with his Hand of the Emperor and Heirsbane abilities, inflicting moderate damage. He will also begin to teleport at random, reseting his enmity and placing himself in melee range to attack the parties healers and ranged DPS. Upon teleporting he will leave the zones of blue fire, so make sure not to run through them.
His most powerful abilities are Judgement: large radius red circle AoE, which will strike for about 1800 damage to anyone caught in the blast radius and a Terminus Est which will create a blue X of energy in the air, which will hang for several moments before firing straight forward in a line.
The fight will end when Gaius's health is reduced to 20%, leading into the fight with Ultima Weapon.
The theme played during this fight is called "Bite of the Black Wolf," composed by Masayoshi Soken. It is an instrumental version of Rise of the White Raven.