From The PSPedia2
Large Ragan breed. Comes to the surface to feed.
Fire Blast(Ground Attack) - De Ragan can launch fireballs at players, causing moderate damage and inflicting Burn.
Fire Blast(Flying Attack) - De Ragan will launch fireballs repeatedly at players while flying, causing moderate damage, knockdown and inflicting Burn.
Charge Attack - When at a certain distance from the De Ragan, it will will charge at players, causing moderatedly high damage and knockback.
Swooping Impact - When the De Ragan is flying, it can swoop after players, causing moderately low damage.
Fire Breath - De Ragan can breath a steady steam of fire as an alternate to fireballs, causing severe damage and inflicting Burn.
Tail Swing - De Ragan can swing at players with its tails, causing knockdown and high damage.
The De Ragan, as a boss, can be pretty difficult to kill if you fail to use caution. When the battle begins, De Ragan usually charge after players, so stand on guard. When this move ends, it will use its moves in a variety of ways. Its best to use melee weapons with fair ATT and high ACC (twin sabers, double sabers, and claws work well). Build a high chain at around 35+, and use photon arts that can hit a single target many times in many spots (Blade Destruction, Gravity Dance, and Infinite Storm are good choices). Remember that if the De Ragan starts to walk, his feet can kick and damage you. When De Ragan are flying, stay on defence. Trying to attack while they are flying can be draining and even fatal. After you deplete a certain amount of its health, it will start using Fire Breath instead of Fireballs. This is very deadly and will kill if you dont avoid it. If your aware of your timing for your attacks and your defence, it wont be long before you defeat the De Ragan.