Here are links to pictures depicting some of the demons you might encounter on Forgotten Kingdoms. Those pictures come from the official site of Wizards of the Coast.
DRETCH (lower right corner of the drawing). This demon look like a squat humanoid with a blubbery, almost hairless body. Its skin is pale white and beige, giving way to sickly blue in some areas. It has a slack and slobbery mouth with many small fangs. It stands about four feet tall.
QUASIT (the small flying creature). This demon is a quasit, a tiny humanoid with spiky horns and bat wings. It stands some two feet tall and seems to weigh around 8 pounds. Its hands and feets are long and slender, with very long, claw-tipped digits. Its skin is pustulent and green.
SUCCUBUS. This demon is a succubus. It is said that succubi often take the appearance of stunningly beautiful female humanoids to lure men into demonic orgies. She has large bat wings and sinister glowing eyes.
BEBILITH. This demon is a bebilith, a huge, predatory arachnid. It looks like a misshapen spider with dark, mottled, chitinous body. Its forelegs end in wicked barbs, and its fanged mouth drips poisonous goo.
RETRIEVER. This demon, a retriever, looks like a huge spider with its four frontmost legs ending in cleaverlike claws.
VROCK (the vulture-like creature). This vrock, a demon, looks like a cross between a large human and a vulture. It is about eight feet tall, with strong, sinewy limbs covered in fine gray feathers and a long neck topped with a vulture's head.
HEZROU (the largest creature). This massive toad-like creature is a hezrou. It looks like a cross between a frog and a human, with arms in place of forelegs. It can walk both upright and on all fours. Its wide mouth has rows of blunt, powerful teeth, and long spines run the length of its back. It is about seven feet tall.
GLABREZU (the large creature with horns). This is a glabrezu, a demon looking much like a towering and well-muscled humanoid with four arms. Two of its arms end in powerful pincers. It has a doglike head with sharp fangs and penetrating violet eyes.
NALFESHNEE. This massive ape-like creature has a boar head as well as small wings on its back, that seem unable to lift its bulk. This is a nalfeshnee.
MARILITH (the creature to the right). This demon, a powerful marilith, looks like a giant snake from the waist down, with green, scaly coils, and attractive female humanoids above the waist. Besides its half-snake body, mariliths are distinguished by their six arms, each one usually holding some exotic weapon and sporting many bangles and jewels. It stands about seven feet tall and measures about 20 feet from head to tip of tail.
BALOR (the creature to the left). This tall red demon is shrouded in flames. It is about 12 feet tall, with red skin and massive, clawed hands. Its huge wings can propel it through the air with unnatural speed.
For more pictures (of various monsters), check there.
Denizens of the Abyss
-
Granel
I've checked Book of Vile Darkness, 3.5e Monster Manual, 3e Monster Manaual 1 and 2, Monsters of Faerun, and the 2e Planescape Monstrous Compendiums 1 and 2 and I didn't see a single creature with 2 dog heads that is a typical Tanar'ri or Demon if you prefer.
What you -might- be thinking of is Demogorgon, the strongest Tanar'ri in the Abyss with the self-given title of "Demon Prince". 3rd Ed's Book of Vile Darkness describes Demongorgon as having two wolf heads and two tentacles that are his arms/attacks. The picture there also shows it but I can't find any 3e pics of him, just older 2e ones that either show him with two lizard heads or two baboon heads.
And if anyone has any questions about Tanar'ri (Demons), or Baatezu (Devils) I'd be more than welcome to answer any private messages. In all my AD&D Nerdlore my strongest points are Planescape.
What you -might- be thinking of is Demogorgon, the strongest Tanar'ri in the Abyss with the self-given title of "Demon Prince". 3rd Ed's Book of Vile Darkness describes Demongorgon as having two wolf heads and two tentacles that are his arms/attacks. The picture there also shows it but I can't find any 3e pics of him, just older 2e ones that either show him with two lizard heads or two baboon heads.
And if anyone has any questions about Tanar'ri (Demons), or Baatezu (Devils) I'd be more than welcome to answer any private messages. In all my AD&D Nerdlore my strongest points are Planescape.
A sapphire haired male aasimar replies to you 'What would you get Tanya for a wedding present?'
You reply to A sapphire haired male aasimar 'A swift kick to the head. '
You reply to A sapphire haired male aasimar 'A swift kick to the head. '
-
Boreas
Also...
Also, if you want to see some of the more powerful demons and devils, you might want to check out the D&D Fiend Folio.... I learned that even balors have nightmares. 
Devils of the Nine Hells
Well, you have read about demons here: http://www.forgottenkingdoms.com/board/ ... php?t=1614
Now lets learn about the chaotic evil demons arch-enemies, the lawful evil devils. These two classes of evil, lower-planes outsiders can sometimes be confused. They both exist on seperate planes of existence, demons existing in the Abyss, devils making their homes in the Nine Hells of Baator. There are also two other names you might hear that are 90% of all devils and demons, demons are called Tanar'ri, devils are also called Baatezu. These two creatures constantly fight in what is called the Blood War, attacking each others homes in a war that has been going on since the planes began, through portals or the River Styx, which connects the two places.
Most demons have a common name, and a more scholarly name, the common name will come first, with the scholarly name second.
Now for individual devils:
LEMURES - (bottom right blob) This creature surges forward, not unlike a molten mass of flesh oozing from the ground. It has a human-shaped head and torso, but its body is a shapeless mass below the waist. A permanent expression of anguish twists across its face. They are about five feet tall and weight closed to 100 pounds.
IMP - (the creature upon the polearm, top right) A tiny humanoid with leather batwings, a barbed tail, and sharp, twisted horns flutters at about eye level, winking into sight out of thin air. They are about two feet tall and weigh about 8 pounds.
BEARDED DEVILS - (lower left) Barbazu. The first thing that stands out about this creature is the massive saw-toothed glaive it carries. The creature's pointed ears and moist, scaly skin mark it as an outsider. It has a long tail, clawed hands and feet, and a snaky, disgusting beard. They stand about six feet tall and weigh about 225 pounds.
CHAIN DEVIL - Kyton. The clanks and rattle of chains announces the arrival of this creature. It appears human in shape and size, but chains wrap it like a shroud, every length ending in a hook or a blade or a heavy ball. The chains seems to slither and slide over the creature's form, almost as if they were alive. They are about six feet tall and weigh near 300 pounds, chains included.
HELLCAT - Bezekira. Silently, with grace and power, a creature emerges on the path ahead. It has the shape of an enormoud lion, but its form consists of blinding light and fiery sparks, as though its body were made of energy and not flesh and bone. They are about nine feet long and weigh close to 900 pounds.
ERINYES - (in the front, to the right) A fierce and beautiful woman, with a statuesque build and flawless skin, stands nearby. She has large, feathery wings and red, glowing eyes. She wields a longsword, and a shining red bow is strapped to her back. Rumor in the underworld tells that the first erinyes were angels who fell from their lofty heights because of some temptation or misdeed. They stand about six feet tall and weigh around 150 pounds.
BONE DEVIL - (smaller creature to the right) Osyluth. This tall creature looks skeletal and wretched, almost a husk of a humanoid form, with dried skin stretched so tight as to outline and emphasize every bone. It has a fearsome, skull-like head and a tail like a scorpion's, and a foul odor of decay hangs in the air around it.
BARBED DEVIL - (spiky creature on left) Hamatula. This creature looks like a tall humanoid covered with sharp barbs, right down to the tip of its long, meaty tail. Its eyes shift and dart about, making it appear agitated or nervous. They are about seven feet tall and weigh closed to 300 pounds.
ICE DEVIL - (creature in the back) Gelugons. This creature looks like a tall, bipedal insect. It has clawed hands and feet, powerful mandibles, and a long, thick tail covered in razor-sharp spikes. They are near twelve feet tall and weigh close to 700 pounds.
HORNED DEVIL - (large creature in the back) Cornugons. This creature is as big as an ogre, with a vaguely humanoid shape. Hideous scales sheathe its body. Huge wings and a snaking, prehensile tail add to its intimidating appearance. They are about nine feet tall and weigh close to 600 pounds.
PIT FIEND - (tall creature in the back) Cloaked in fire and as tall as two humans, this hulking monster spreads its batlike wings and cracks its whiplike tail. Great scales cover its body like armor. It smiles, revealing large fangs that drip with hissing venom. These are the undisputed lords of the baatezu, masters of creating fear in mortals and devils alike. Pit fiends are near twelve feet tall and weigh close to 800 pounds.
Well, thats enough nightmares for today, if I missed anything or you think perhaps something should be added, please tell me.
Thanks,
Now lets learn about the chaotic evil demons arch-enemies, the lawful evil devils. These two classes of evil, lower-planes outsiders can sometimes be confused. They both exist on seperate planes of existence, demons existing in the Abyss, devils making their homes in the Nine Hells of Baator. There are also two other names you might hear that are 90% of all devils and demons, demons are called Tanar'ri, devils are also called Baatezu. These two creatures constantly fight in what is called the Blood War, attacking each others homes in a war that has been going on since the planes began, through portals or the River Styx, which connects the two places.
Most demons have a common name, and a more scholarly name, the common name will come first, with the scholarly name second.
Now for individual devils:
LEMURES - (bottom right blob) This creature surges forward, not unlike a molten mass of flesh oozing from the ground. It has a human-shaped head and torso, but its body is a shapeless mass below the waist. A permanent expression of anguish twists across its face. They are about five feet tall and weight closed to 100 pounds.
IMP - (the creature upon the polearm, top right) A tiny humanoid with leather batwings, a barbed tail, and sharp, twisted horns flutters at about eye level, winking into sight out of thin air. They are about two feet tall and weigh about 8 pounds.
BEARDED DEVILS - (lower left) Barbazu. The first thing that stands out about this creature is the massive saw-toothed glaive it carries. The creature's pointed ears and moist, scaly skin mark it as an outsider. It has a long tail, clawed hands and feet, and a snaky, disgusting beard. They stand about six feet tall and weigh about 225 pounds.
CHAIN DEVIL - Kyton. The clanks and rattle of chains announces the arrival of this creature. It appears human in shape and size, but chains wrap it like a shroud, every length ending in a hook or a blade or a heavy ball. The chains seems to slither and slide over the creature's form, almost as if they were alive. They are about six feet tall and weigh near 300 pounds, chains included.
HELLCAT - Bezekira. Silently, with grace and power, a creature emerges on the path ahead. It has the shape of an enormoud lion, but its form consists of blinding light and fiery sparks, as though its body were made of energy and not flesh and bone. They are about nine feet long and weigh close to 900 pounds.
ERINYES - (in the front, to the right) A fierce and beautiful woman, with a statuesque build and flawless skin, stands nearby. She has large, feathery wings and red, glowing eyes. She wields a longsword, and a shining red bow is strapped to her back. Rumor in the underworld tells that the first erinyes were angels who fell from their lofty heights because of some temptation or misdeed. They stand about six feet tall and weigh around 150 pounds.
BONE DEVIL - (smaller creature to the right) Osyluth. This tall creature looks skeletal and wretched, almost a husk of a humanoid form, with dried skin stretched so tight as to outline and emphasize every bone. It has a fearsome, skull-like head and a tail like a scorpion's, and a foul odor of decay hangs in the air around it.
BARBED DEVIL - (spiky creature on left) Hamatula. This creature looks like a tall humanoid covered with sharp barbs, right down to the tip of its long, meaty tail. Its eyes shift and dart about, making it appear agitated or nervous. They are about seven feet tall and weigh closed to 300 pounds.
ICE DEVIL - (creature in the back) Gelugons. This creature looks like a tall, bipedal insect. It has clawed hands and feet, powerful mandibles, and a long, thick tail covered in razor-sharp spikes. They are near twelve feet tall and weigh close to 700 pounds.
HORNED DEVIL - (large creature in the back) Cornugons. This creature is as big as an ogre, with a vaguely humanoid shape. Hideous scales sheathe its body. Huge wings and a snaking, prehensile tail add to its intimidating appearance. They are about nine feet tall and weigh close to 600 pounds.
PIT FIEND - (tall creature in the back) Cloaked in fire and as tall as two humans, this hulking monster spreads its batlike wings and cracks its whiplike tail. Great scales cover its body like armor. It smiles, revealing large fangs that drip with hissing venom. These are the undisputed lords of the baatezu, masters of creating fear in mortals and devils alike. Pit fiends are near twelve feet tall and weigh close to 800 pounds.
Well, thats enough nightmares for today, if I missed anything or you think perhaps something should be added, please tell me.
Thanks,
Glim asks Gwain 'Can I be on the watch?!?'
Gwain raises an eyebrow.
Gwain seems to display a look of complete horror for a second...
Gwain raises an eyebrow.
Gwain seems to display a look of complete horror for a second...