Belias, the Gigas
Bestiary Description
“Scion of darkness and guardian of the Holy Realm, made by the gods in opposition to the Transcendant Loghrif, scion of light.
Called the Gigas for his appearance: man and monster fused as one.
Considered a mistake upon his making, and receiving not his intended role, the Gigas challenged the gods and lost. Scorned by his masters, he found another, the Dynast-King, whose tomb he swore to protect for eternity”
Belias is fought during a regular playthrough of the game when the team reaches the Tomb of King Raithwall. He must be fought and obtained in order for the team to reach the Dawn Shard.
He is the first Esper that the team obtains. He also plays a role in the story when the team reaches the entrance to the Ancient City of Giruvegan.
Location
Belias is located in the Cloister of Flame zone of the Tomb of King Raithwall.
Esper Battle
Level: 20
HP: 15,943
Steal: 
Aries Gem (55%), 
Ether (10%), High Archana (3%)
Belias is an Esper, the first one that you have encountered so far, and he is responsible for guarding the Dawn Shard.
He is a fire-based Esper and most of his damage will come from fire-based Magick spells. Do not use fire-based Magick such as 
Fire on him as it will heal him instead of inflicting damage. The most effect spell to use against him is Aqua. Belias is susceptible to 
Slow so be sure to try and inflict it early on in the fight.
You should also cast 
Shell on each of your party members to minimize the amount of damage done and be sure to remove the Oil status effect if any of your party members are afflicted as this will cause increased damage from fire-based attacks. His Firaja spell has a chance to inflict the Oil status effect.
A video of the battle in the Zodiac Age version is included below:
Congratulations – you now have Belias as an Esper which you can use in battle!
Belias is similar to Ifrit in previous Final Fantasy titles. His attacks are Fire-based. His standard attack is called Painflare and his ultimate attack is called Hellfire (which hits all enemies in range).
Esper Locked Licenses
Unlocking Belias on the License Boards of certain jobs will unlock additional License Boards:
There are no optimal choices for the Licenses that can be unlocked using Belias, but 
Libra can be somewhat helpful.