How's this for the Special Attacks, mostly based on the Titanic template's SAs. We'll need to figure out some trample and area multiple values.
Special Attacks
A mystaran gargantua creature retains the special attacks of the base creature and also gains the abilities and modifications described below. The DCs of its special attacks are recalculated according to its new hit dice and ability scores.
Area Attacks (Ex): A mystaran gargantua creature's area attacks (such as a spider’s ability to generate webs) increase in size to gigantic proportions. Multiply the height, width, and length of the base creature's area attack by the area modifier given on the Mystaran Gargantua Modifiers table.
Increased Damage (Ex): If the base creature has a special attack that deals hit point damage, increase this damage according to the Mystaran Gargantua Damage table, or multiply by 4 if the attack does a set amount of damage (e.g. if the base creature has an special attack doing 4 points of acid damage the mystaran gargantua's version would do 16 acid damage.)
If the base creature has a special attack that causes ability damage or ability drain, such as a poison bite, increase this ability damage by the amount given in the Mystaran Gargantua Modifiers table.
Swallow Whole (Ex): A mystaran gargantua gains a swallow whole attack if it ha a bite attack and is Gargantuan size or larger. The creature can swallow opponents up to three size smaller than itself (i.e. up to the size of the base creature) by making a successful grapple check. Once inside, an opponent takes takes crushing damage equal to the creature's bite attack plus acid damage (8 plus 4 per size above Gargantuan) from the creature's gizzard. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the gizzard (AC 10 plus half the creature's natural armour). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. A Gargantua's interior can hold 2 opponents of the base creature's size, 8 opponents 1 size smaller than the base creature, 32 opponents 2 sizes smaller, and so on.
If the base creature already has a swallow whole attack, use that attack's damage values (adjusted by the Increased Damage special ability) if the result would be better than the damage given above.
Trample (Ex): A Huge or larger mystaran gargantua gains a trample attack. It can trample opponents smaller size than itself, doing the damage given in the Mystaran Gargantua Modifiers table plus 1½ times the creature's Strength bonus. A trampled opponent can attempt either an attack of opportunity at a –4 penalty or a Reflex save (DC 10 + ½HD + the titanic creature’s Str bonus) for half damage.
If the base creature already has a trample attack, use that attack's damage value adjusted by the Increased Damage special ability if the result is better than the damage of the Mystaran Gargantua Modifiers table.
