Nefarox, Overlord of Grixis

Nefarox, Overlord of Grixis

CR 28 XP: 4,915,200
CE Colossal outsider (Chaotic, Demon, Extraplanar, Evil)
Init -1; Senses telepathy; Perception +51
AC 37, touch 1, flat-footed 37 (-8 size, +36 natural, -1 Dex)
HP 888 (48d8+672); fast healing 20
Fort +40, Ref +25, Will +26
Defensive Abilities demon traits; DR 15/epic; Immune disease, electricity, fire and poison; SR 34; Resist acid 10, cold 10, and fire 10
Speed 80 ft.
Melee 2 slams +87 (2d8+38), bite +63(4d6+28, crit 19-20 +1d6), 2 gores +81 (4d6+38)
Space 100 ft., Reach 100 ft.
Special Attacks Breath weapon, roar, swallow whole, tattoos, trample (2d8+28)
Before Combat On the battlefield, Nefarox just grabs and eat whatever they can, regardless of whether the victim is friend or foe. Inside of its mouth are always vrocks that pick at the livers of the entrapped celestials, caught in the demon’s teeth. Occasionally, they take to wing, to rain their own brand of destruction below. Nefarox attacks are considered chaotic, epic and evil for purposes of overcoming damage reduction.
During Combat A demon’s natural weapons, as well as any weapon it wields, is treated as chaotic and evil for the purpose of resolving damage reduction
Str 48, Dex 8, Con 38, Int 5, Wis 11, Cha 10
Base Atk +48; CMB +75; CMD 84
Feats Awesome Blow, Blind-Fight, Cleave, Great Cleave, Improved Bull Rush, Improved Critical (Bite), Improved Sunder, Overwhelming Critical, Power Attack, Snatch, Weapon Focus (Bite, Slam)
Skills Acrobatics +70, Climb +70, Perception +51
Languages Abyssal, Celestial, and Draconic, telepathy
Environment the Abyss
Organization Solitary plus 6-10 vrocks, Pair, Troop (3-6)
Treasure None
Breath Weapon (Su) These walking mountains unleash a cloud of venomous poison functioning as a storm of vengeance lasting for 10 rounds. The Nefarox use their breath weapon once every 1d12 rounds. This ability functions as the spell cast by a 20th-level caster.
Roar (Ex) Once every 1d4 rounds, Nefarox may release a deafening roar, affecting all non-evil living creatures within 240 feet. All legitimate targets in the area must attempt Will saves (DC 34) or become panicked. Nefarox’s roar also deafens targets within 30 feet who fail their save. The save DC is Charisma-based.
Swallow Whole (Ex) If Nefarox achieves a pin against a size Gargantuan creature or smaller with its snatch attack, it may swallow the victim whole, by making a successful grapple check. Once inside Nefarox, the opponent takes 4d6+19 points of acid damage and 2d6 points of fire damage from the demon’s digestive process. Three successful grapple checks allow the swallowed creature to Climb out of the stomach, and return to Nefarox’s maw, where another successful grapple check is required to break free. Swallowed victims cannot cut their way out of Nefarox’s stomach, as its stomach muscles immediately close any wounds made. Nefarox’s maw can hold 2 Gargantuan creatures, 8 Large creatures, 32 Medium creatures or 128 Small or smaller opponents. These are in addition to the vrock who lurk there as well.
Tattos (Sp) Blasphemous tattoos cover the whole of Nefarox’s body. Every round as a free action, one of the tattoos flares, as per blasphemy cast by a 20th-level caster. 
Trample (Ex) Nefarox deasl the indicated damage on trample attacks, essentially anytime they move through occupied squares. Targets of this attack may attempt attacks of opportunity, but at a -4 penalty. If they opt not to take the attack of opportunity, they may attempt a Reflex save (DC 53) and take half the indicated damage.
Summon (Sp) Demons share the ability to summon others of their kind, typically another of their type or a small number of less powerful demons.
Emerging from the mists of the battlefield is a 300-foot tall demon bleeding violet ichor from innumerable rents in its ebon flesh. Its great shaggy head sports 666 eyes and 666 horns. From its maw, a hole so dark and so rancid that the smell of it is contagion, emerge flights of vrocks swarming around its rows of teeth, feasting on the rotting celestial flesh caught therein. Over all of its body are blasphemous runes, inverted holy symbols of the good gods, which flash with life every time the giant demon moves.
Nefarox is the demonic Lord of Grixis. He became the head of the shard after Malfegor's death. Nefarox is large enough to be a layer of the Abyss unto itself. As creatures of mind-boggling size, they represent the worst threat posed by this chaotic plane. No one knows if there are others and how many exist, how and what they eat, or what drives these foul creatures. What sages and demonologists do know is that Nefarox sleep, awaiting the end of the world, for when the last days come to mortals, Nefarox shall awake and devour the universe. Thankfully, they remain asleep, as they have for countless millennia.
Occasionally, when the need is most dire, a group of 6 balors descends to the darkest pit known in the Abyss and awakens just one of the sleepers.
Source: Originally from the Book of Fiends Designed By Aaron Loeb, Erik Mona, Chris Pramas, and Robert J. Schwalb, MTG Magic 2013 cd 103