Tamiel is the fourth Grigori you fight in the game, and is fought on the Purgatorium at Roak. It is likely to be the hardest battle the party has fought so far.
Tamiel appears as a man in robes with a staff. He is constantly surround by henchmen which are easily defeated by Edge or Bacchus, as their strong attacks are good against the henchmen's low HP. Tamiel's main attacks are aerial symbology attacks, like orbs or a shroud of darkness which follows the player. His attacks are powerful, particularly his laser attack which deals around 1500+. The party needs to remain healed or one death could lose the whole battle. His defense is quite high and physical attacks don't do a lot of damage. The key to the battle is to keep a constant flow of attacks so he doesn't have a chance to counter. Having Bacchus use Force Breaker and Irradiation are a good combo to use against him. Edge's combos are also effective against him. Another key point is that you have to be levelled, if you are low levelled then it will be very hard to defeat him. His attacks do a lot of damage so you need a lot of health and powerful attacks to counter his. if you have any EM bombs, towards the end of the battle use them as they deal 2500 damage and could be the finishing blow.