The use of Tortoise song will dispel 3 buffs, including food, to all within 20'
Casts various Earth and Water elemental magic, including -ga V
Head Butt knocks back quite far, and applies a powerful Defense Down debuff. Uses multiple times in quick succession
Harden Shell grants a significant reduction in damage taken until dispelled.
Earth Breath has a 3 second charge-up time. Can easily move to side as a tank to avoid getting hit for full damage.
Aqua Breath is nearly instant, but deals less damage than Earth breath (about half).
At 75%, 50%, 25%, 10%, and 5%, it will retreat within its shell and regenerate at an accelerated rate for about 20% of its total life
Magic bursting with Blizzard while in its shell will stagger (white!!) and force it to come out
Upon exiting its shell, it will DRAW-IN everyone right in front followed by a Breath Attack. Damage can be avoided by quickly running from it, but movement is hindered from running through/into other players and the TP move is sometimes instant
If he chooses Earth Breath, if the tank can sidestep fast enough, he can prevent the party/alliance from getting hurt at all if he moves quickly. Due to player collision, needing everyone to move at the same time may he difficult.
If he chooses Aqua Breath, it should be survivable assuming everyone is topped off, and has a good -DT setup. Stoneskin as well would prevent anyone from dying. Aqua Breath is still nearly instant.