An upcoming boss fight sees the PC fight a darkfathom (see below), a homebrew creature based on this miniature. The encounter will take place in the darkfathom's underwater lair, a large chamber containing a few statues that the darkfathom can command to become animate if need be. Its lair is entered through a labyrinth of smaller chambers into which the PCs can retreat. The darkfathom has been scrying on the PCs for some time and knows their strengths and weaknesses.
The ten PCs are a duskblade, knight, rogue, sorcerer, and warlock that are each level 6, and a bard, dragon shaman, fighter, ranger, and werebear that are each level 7. The PCs will have magically gained freedom of movement and water breathing effects as well as swim speeds.
Gargantuan Outsider (augmented dragon)
Hit Dice: 22d12+154 (297 hp)
Initiative: +4 (−1 Dex)
Speed: 60 ft., swim 60 ft.
AC: 28 (−2 size +21 natural −1 Dex), flat-footed 28, touch 9
Base Attack/Grapple: +22/+42
Attack: Bite +28 (4d8+12)
Full Attack: Bite +28 (4d8+12), tail slap +28 (2d8+12), 2 claws +28 (2d8+4), 2 minor tails +28 (2d8+4), 2 major tails +28 (2d8+4)
Space/Reach: 20 ft./15 ft. (20 ft. bite)
Special Attacks: breath weapon, crush, spell-like abilities, spells, tail sweep
Special Qualities: blindsense 60 ft., darkvision 120 ft., DR 10/magic, frightful presence, immunity to sleep effects, immunity to paralysis effects, immunity to acid, keen senses, SR 21
Saves: Fort +21, Ref +12, Will +17
Abilities: Str 27, Dex 8, Con 27, Int 14, Wis 15, Cha 14
Skills: 200 skill points include 25 ranks in the skills Hide, Move Silently, and Swim, and 12 ranks each in the skills Diplomacy, Intimidate, Knowledge (arcana), Knowledge (the planes), and Sense Motive
Feats: Darkfathom Tail [see below], Multiattack (MM 304), Improved Multiattack (Dungeon #109 49), Iron Will (PH 97), Quicken Spell (PH 98), Rapid Breath (SS 39), Shape Breath (Dr 73), World Weary (Dragon #319 61)
Challenge Rating: 16?
Alignment: Chaotic Evil
Spells Known (6/7/5; CL 5; base save DC = 12 + spell level): 0—detect magic, daze, light, mage hand, ray of frost, read magic; 1st—color spray, magic missile, protection from good, shocking grasp; 2nd—pressure sphere, resist energy.
Breath Weapon (Su): It can every 1d4 rounds take a standard action to use its breath weapon. Creatures in a 120-ft. line make Ref saves (DC 29). Failure means that the creature is dealt 14d4 points of cold damage while success means that the creature's dealt half damage. It can instead every 1d4+1 rounds use its breath weapon as a 60-ft. cone.
Crush (Ex): It can take a standard action while jumping or flying to land. Medium or littler creatures caught in its space make Ref saving throws (DC 29). Failure means that until it ceases to occupy the creature's space, the creature is pinned and dealt 4d6+12 budgeoning damage each round.
Frightful Presence (Ex): When it attacks, charges, or swims overhead, creatures within a 210-ft. radius that have fewer than 22 HD make Will saves (DC 23). Failure by a creature that possesses 4 HD or less means that the creature for 4d6 rounds is panicked. Failure by a creature that possesses more than 4 HD means that the for 4d6 rounds the creature is shaken. Success means that for 24 hours the creature is immune to its frightful presence.
Keen Senses (Ex): It sees four times as well a human in shadowy illumination and twice as well in normal light.
Spell-like Abilities: 1/day—corrupt water, darkness.
Tail Sweep (Ex): It can take a standard action to make a tail sweep. Small or littler creatures within a 30-ft. half-circle extending from an intersection on the edge of its space in any direction make Ref saves (DC 29). Failure means that the creature's dealt 2d6+12 points of damage while success means that the creature's dealt half damage.
Note: The feat Darkfathom Tail gives it 1 extra tail with which it can make additional tail attacks as per the stat block.