Crystal Screamer (CR 16)

Gargantuan Magical Beast
Alignment: Often neutral
Initiative: +5 (+1 Dex, +4 Improved Initiative); Senses: blindsight and Listen +33

AC: 23 (-4 size, +1 Dex, +16 natural), touch 7, flat-footed 22
Hit Dice: 36d10+180 (378 hp)
Fort +27, Ref +23, Will +15
Speed: 30 ft., burrow 15 ft.
Space: 20 ft./10 ft.
Base Attack +36; Grapple +44
Attack: Bite +41 melee
Full Attack: Bite +41 melee
Damage: Bite 4d6+13
Special Attacks/Actions: Sonic scream +37 ranged touch
Abilities: Str 28, Dex 12, Con 21, Int 6, Wis 12, Cha 12
Special Qualities: fast healing 5, immunities, burrow, SR 26
Feats: Cleave; Great Fortitude; Improved Initiative; Iron Will; Lightning Reflexes; Power Attack
Skills: Hide -11 and Listen +33
Advancement: 37-72 HD (Gargantuan)
Climate/Terrain: Any land or underground
Organization: Solitary or clutch (2-4)
Treasure/Possessions: None

Source: Bastion of Broken Souls

Sonic Scream (Su): Every 2 rounds, a crystal screamer can focus sonic energy in a ray up to 60 feet long. This is a ranged touch attack that deals 18d6 points of damage to a single target. If it so chooses, it can instead scream at a crystal tree (or the ground, if not in the Bastion of Unborn Souls) to create an explosion of shattered crystal. This attack deals 9d6 points of piercing damage to all within 10 feet of the effect's center and destroys all the crystal trees in the same radius, regardless of their hardness and hit points.

Burrow (Su): By creating a special audible resonance, crystal screamers can burrow through the substance of the Bastion of Unborn Souls (solidified positive energy). They do not leave holes behind, so other creatures cannot follow them. This ability does not allow them to actually leave (or enter) the mystically sealed Bastion, only burrow within its confines.

Immunities (Ex): Crystal screamers are immune to sonic attacks and effects. If a sonic attack that deals damage is directed at a crystal screamer, the attack is reflected back at the originator, its damage potential doubled.

A crystal screamer whose sense of hearing is impaired is effectively blinded and treats all targets as having total concealment (see Concealment).

A crystal screamer alternates between its sonic attack and devastating bite.