Yhidothrus

ray of enfeeblement 3/day, gentle repose 2/day, or slow 1/day

Once per day, you can use a powerful bestow curse, heightened to a 7th-level spell. This special curse causes the creature cursed to suddenly grow to venerable age. This curse imparts a –6 penalty to Strength, Dexterity, and Constitution, but does not grant any bonus to Intelligence, Wisdom, or Charisma. This ability is the equivalent of a 7th-level spell.

You can use summon monster IX once per day, but only to summon one advanced fiendish purple worm.

corrosive touch 3/day, acid arrow 2/day, or vampiric touch 1/day

You can crawl beneath the surface of the earth like a worm and then burst forth to horrify foes. You gain a burrow speed of 30 feet, which can be used only in mud, sand, soil, or other soft substances (not solid stone). You gain a +10 bonus on Stealth checks while burrowing. Once per hour, if you take a standard action to emerge from burrowing with a roar and spray of soil, each creature within 30 feet of your emergence that was not aware of your presence must succeed at a Will save (DC = 10 + half your Hit Dice + your Charisma modifier) or be shaken and stunned for 1 round and shaken for 2d4 rounds thereafter. The burrowing ability is an extraordinary ability, but the latter part of the ability is a supernatural, mind-affecting fear effect.

As a result of your practice of sleeping in parasite-infested mud or soil to fulfill your obedience to Yhidothrus, your flesh has become riddled with an unholy infection. Yet far from being a troublesome condition, these worms are a welcome addition to your life, and as you gain this final boon, your body is devoured from the inside out by a mass of wriggling leeches, maggots, worms, and other horrid vermin, which are thereafter bound together into a cohesive whole by your foul will. When you attain this boon, you become a worm that walks. When your emergence (see above) causes creatures to become shaken, those creatures are also sickened for 1 minute.

ray of enfeeblement 3/day, gentle repose 2/day, or slow 1/day

Once per day, you can cast a powerful bestow curse, heightened to a 7th-level spell, as a spell-like ability. This special curse causes the target creature to suddenly advance to venerable age. This curse imposes a –6 penalty to the target’s Strength, Dexterity, and Constitution scores, but its Intelligence, Wisdom, or Charisma scores do not increase. These penalties do not stack with any existing penalties a creature might already have as the result of advanced age.

By placing a hand upon the ground and whispering a series of blasphemies to the Ravager Worm, you can call up from below an immense and destructive manifestation of your fiendish lord. You can cast summon monster IX once per day as a spell-like ability to summon one advanced fiendish purple worm.

expeditious retreat 3/day, silence 2/day, or sands of time 1/day

As a swift action when you confirm a critical hit with a weapon against a living foe, instead of dealing the additional damage from the critical hit, you can instead deal normal damage and force the target to attempt a Fortitude save (DC = 10 + half your Hit Dice + your Charisma modifier). On a failed save, the target painfully advances in years to the next age category. This aging can never have beneficial effects (such as if used against a true dragon). The target gains the penalties associated with the new age category to its Strength, Dexterity, and Constitution scores, but its Intelligence, Wisdom, or Charisma scores do not increase. This advanced age effect lasts for 24 hours before it fades and the affected creature returns to its normal age. A venerable creature (including one whose age has been magically accelerated via this ability to venerable, but not one whose age is temporarily advanced from other effects, such as per sands of time) that fails its saving throw against the aging effects of this ability is instantly slain, as if via old age (though the body instantly reverts to its original age appearance upon death). A creature slain by this effect can only be restored to life via miracle, reincarnate, true resurrection, or wish. This is a curse effect.

You can call upon the Ravager Worm to temporarily consume time itself in an area surrounding you. You can cast time stop once per day as a spell-like ability. When you use this ability, those in the area of effect are subjected to a powerful vision—that the world they are in becomes wrapped in the endless coils of the Ravager Worm. The affected creatures never glimpse Yhidothrus’s head, and know only for the brief instant of eternity they spend in your time stop area that the world around them is fully wrapped in the coils of something more foul than they even imagined.