Spawn Calling

Conjuration (Calling) [chaotic, evil]
Level: Cleric */Oracle * 9, Sorcerer */Wizard * 9, Warlock * 9
Components: V, S, M/DF (bull's blood, tallow, one or more humanoid victims totaling at least 15 Hit Dice)
Casting Time: 1 week
Range: medium (100 ft. + 10 ft./level)
Duration: instantaneous
Saving Throw: None
Spell Resistance: no
  Having attained the highest and most profane form of magical achievement in the Great Destroyer's service, you are able to call forth his most dreaded creations: the Spawn of Rovagug.
  Casting this spell requires a week-long ritual involving the sacrifice of one or more sentient humanoid creatures that between them possess a total of at least 15 Hit Dice. You may not eat, sleep, or cast any other spells for the duration of this ritual. After the third day of the ritual, you must succeed at a Constitution check on each remaining day of the ritual (DC 10 + 1 for each previous check) or take 1d6 points of nonlethal damage from hunger. At the end of the ritual, you gain the Exhausted condition from lack of sleep.
  Upon completion of the ritual, the ground rumbles in a 100- foot radius centered on you. This effect lasts for 1 round. Any creature on the ground in this area that attempts to cast a spell during this round must succeed at a concentration check (DC 20 + spell level) or lose the spell. Any creature on the ground in the area that attempts to attack or move during this round must succeed at a DC 15 Reflex Save at the beginning of its turn or fall Prone.
  At the beginning of your next turn, a massive fissure full of dark fire and shrieking cries appears at a point you designate within the spell's range, and a Spawn of Rovagug emerges.
  This creature takes the form of a thunder behemoth (Pathfinder RPG Bestiary 3 39) with the advanced and entropic simple templates. Unlike with summon monster or similar spells, the caster has no control whatsoever over the called creature. The spawn immediately heads in a random direction or toward an obvious target such as a population center, destroying anything in its path, yourself and your allies included.
  Any creature may attempt to control the called Spawn of Rovagug via spells like dominate monster or binding.
  However, if such an attempt fails, it draws the spawn's attention, and the monster immediately tries to destroy the creature that attempted to control it.
  Because the Spawn of Rovagug are all magical beasts native to the Material Plane, spells such as banishment or dismissal have no effect on the called spawn.