There are special rules for the summoning of Daemons found on page 62 of Codex: Chaos. Daemons are summoned during any psychic phase by expending summoning points. They are summoned at the very end of the psychic phase, after any powers have been used. It requires 2 summoning points to summon a daemon, and 10 summoning points to summon a Greater Daemon. Any points you do not use can be saved and used in a later psychic phase. With the exception of Greater Daemons, which are treated as characters, you must summon Daemons in units of at least three.
Possessing Models
A Daemon model may possess any other model within the Chaos Space Marine army which bears its Mark of Chaos. A Greater Daemon can only possess a Chaos Champion, Chaos Sorcerer, or Chaos Lord that bears their Mark. The model that is possessed is killed and counted as a casualty for Victory Points and adds to your opponent's Victory Point total. Models that are lost in this way are not counted as casualties for the purpose of forcing a unit to take a Break test.
Possessing Teleporting Troops
Troops other than Chaos troops run the risk of being possessed each time they teleport if their are any Daemons still awaiting summoning by the Chaos player. Grey Knights and Inquisitors of the Ordo Malleus are immune to this.
Daemon Banishment
Daemons are banished back into The Warp if all models bearing their Mark are killed. This means it is fairly silly to possess the last model in the army bearing the Chaos Mark, because it is killed by this possession and all Daemons bearing that Mark, including the one doing the possessing, will be banished into the Warp.
Daemon Psychic Powers
Greater Daemons do not draw psychic power cards, as they have all four powers of their Chaos God. The cards are left to the Chaos Sorcerers to use.
Important: You should familiarize yourself with all the special rules for the use of Daemons on pages 61-67 of Codex: Chaos, as there are many special rules, vulnerabilities, and immunities that affect the way Daemons are used on the battlefield.
Bloodthirsters
A Bloodthirster carries two weapons: an Axe of Khorne and a Long Barbed Lash. The Axe is an enchanted Daemon Weapon. Although Bloodthirsters have no magic, they are exceptionally strong and savage.
Special Rules
Greater Daemon: All the special rules for Daemons apply as described in the Chaos Daemon section of Codex: Chaos.
Terror: Bloodthirsters cause Terror as per the terror rules in the psychology section of the Warhammer 40,000 rulebook. Remember that creatures that cause terror also cause fear.
Chaos Armour: Chaos Armour gives a 3+ save, and because this is armour rather than a Daemonic Aura, magic weapons don't cancel out the Bloodthirster's armour save.
Axe of Khorne: The Bloodthirster carries a mighty Axe of Khorne which does not 1 wound on its victim, but d3 wounds.
Fly: The Bloodthirster has wings and can fly as described in the Warhammer 40,000 rulebook.
Juggernauts of Khorne
Juggernauts are ridden into battle by Khorne's most favoured followers. They are great beast whose flesh is made of brass and whose blood is pure fire, brutal and viscous in their attack.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. The Juggernaut has a Daemonic save of 4+ on a d6.
Fear: Juggernauts cause fear as described in the Warhammer 40,000 rulebook.
Bloodletters of Khorne
The Hordes of Khorne are made up of countless ferocious Bloodletters, Bloodletters have scaly red hides and shiny red claws. They are viscious fighters, with murderous talons, but their most fearsome weapon are their Hellblades.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. The Bloodletter has a Daemonic save of 4+ on a d6.
Fear: Bloodletters cause fear as described in the Warhammer 40,000 rulebook.
Hellblade: The Hellblade drips with blood and is rich with enchantment. A hit from the Hellblade causes not 1 wound but d3 wounds to its victim.
Fleshhounds of Khorne
Fleshhounds are huge, daemonic hounds, with heavy heads that are both reptilian and savagely canine. Their hide is tough and ruddy and their claws are dark with blood. Each Flesh Hound wears a Collar of Khorne around its neck to protect it from magic.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. The Flesh Hound has a Daemonic save of 4+ on a d6.
Fear: Flesh Hounds cause fear as described in the Warhammer 40,000 rulebook.
Flesh Hounds' Collar of Khorne: The Collar absorbs and nullifies other enchantments. Magic weapons can not hurt a Flesh Hound at all, and spells cast against them are automatically dispelled and will not work.
Keeper of Secrets
The Keepers of Secrets are possibly the most enthraling of all Daemons. Highly intellegent, whose silvered words and languid gestures bely their true power.
Special Rules
Aura of Slaanesh: Enemies in base-to-base contact with a Keeper of Secrets must pass a Ld test on 2d6 to be able to attack, you must test for each model fighting the Daemon, and this test must be taken at the start of each combat round.
Greater Daemon: All the special rules for Daemons apply as described in the Chaos Daemon section of Codex: Chaos.
Terror: Keepers of Secrets cause Terror as per the terror rules in the psychology section of the Warhammer 40,000 rulebook. Remember that creatures that cause terror also cause fear.
Magic: The Keeper of Secrets is a sorcerer with a magic level of 4, and may draw four spells from the Slaanesh deck.
Daemonettes of Slaanesh
Daemonettes are quick, and agile fighters, with clawed hands that can slice through flesh and pierce armour. They have a perverse and unnatural beauty.
Special Rules
Daemons: All of the special rules for Daemons apply as described in the Codex: Chaos. Daemonettes have a Daemonic save of 4+ on a d6.
Fear: Daemonettes cause fear as described in the Warhammer 40,000 rulebook.
Magic: A unit of Daemonettes has a magic level and can cast spells like a wizard. The size of the unit defines its magic level and the number of spells it has. 1-5 models = magic level 1 / 1 spell. 6-10 models = magic level 2 / 2 spell. 11-15 models = magic level 3/ 3 spell. 16+ models = magic level 4 / 4 spell.
Fiends of Slaanesh
Fiends of Slaanesh are bizzare Daemons, a mixture of scorpion, reptile, and human. They can lash out with their tale to strike and stab their opponents. they exude a strong, sweet, soporific musk that overwhelms their close combat opponents with intense drowsiness.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Fiends have a Daemonic save of 4+ on a d6.
Fear: Fiends of Slaanesh cause fear as described in the Warhammer 40,000 rulebook.
Scorpion Tail: They have 3 Attacks, one of which is from its long. barbed tail. Work out the tail attack separately. If the tail hits, then take any armour savings throw for the victim immediately, if this save fails the target takes 1 wound automatically. You do not roll to wound.
Soporific Musk: Enemy models in base-to-base contact with a Fiend deducts -1 from all to hit rolls.
Steeds of Slaanesh
The Steeds of Slaanesh are weird bipedal beasts that are ridden into battle by either Champions of Slaanesh or Daemonettes.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Steeds have a Daemonic save of 4+ on a d6.
Fear: Steeds of Slaanesh cause fear as described in the Warhammer 40,000 rulebook.
Tongue Attack: The Steed has a single Attack, which is made with its tongue. Work this attack out as follows: Roll to hit. If the target is hit, it is ensnared, and dragged before the rider. Complete the attack using the rider's weapon and Strength value as if it were the rider that struck the blow. If the enemy is not slain, then he has struggled free and can continue to fight as normal.
Great Unclean One (GUCO)
The Great Unclean One is covered with sores and boils and has a leprous skin. Slime and puss oozes from his many sores and boils, decaying organs protrude from rents in its rancid flesh.
Special Rules
Greater Daemon: All the special rules for Daemons apply as described in the Chaos Daemon section of Codex: Chaos.
Terror: Great Unclean Ones cause Terror as per the terror rules in the psychology section of the Warhammer 40,000 rulebook. Remember that creatures that cause terror also cause fear.
Stream of Corruption: This is worked out in the shooting phase. The extent of the vomit is indicated using the extended teardrop shaped template, the same one used for dragon flame and fire attacks. Position the template in front of the Daemon so that the broad end covers the target and the narrow end touches the Daemon. Every model under the template must attempt to dive aside in order to avoid the vomit. To do this, they must roll equal to or less than their Initiative on a d6. A roll of 6 always fails. If it fails, the target automatically takes one wound, with no armour save.
Magic: The Great Unclean One is a sorcerer with a magic level of 4, and may draw four spells from the Nurgle deck.
Beasts of Nurgle
The Beasts of Nurgle are gigantic and sluglike, their heads are topped by a fringe of fat tentacles, from which oozees a paralizing slime. They also leave a slimy trail behind them as they move, like a slug or snail.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Beasts of Nurgle have a Daemonic save of 4+ on a d6.
Fear: Beasts of Nurgle cause fear as described in the Warhammer 40,000 rulebook.
Attacks: The Beast has d6 attacks from its tentacles, determined during each hand to hand combat round. The Slime will automatically penetrate the target's armour, so no armour save is allowed.
Slime Trail: The Beast leaves a slime trail behind it as it moves, this means it is impossible to attack the beast from the side or rear without touching the slime. Any model attempting to attack the Beast from the side or rear will sustain a single automatic hit, as if it had been struck by the Beast itself. Work this out before the attacker's own blows are struck.
Plaguebearers of Nurgle
Plaguebearers are created from all those who died of the Dreaded disease Nurgle's Rot. Plaguebearer's are also called Nurgle's Tallymen because it is their job to keep count of all the many diseases and corruptions their Master visits upon the Worlds.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Plaguebearers have a Daemonic save of 4+ on a d6.
Fear: Plaguebearers cause fear as described in the Warhammer 40,000 rulebook.
Plaguesword: The Plaguesword drips venomous slime. If the target has more than one wound, than a wound from this weapon will kill mortal creatures on a d6 roll of 4 or more regardless of how many wounds the target can normally sustain. This only applies to mortal creatures, not Daemons.
Cloud of Flies: Plaguebearers are surrounded by a dense black cloud of foul buzzing flies. This terrible distraction means that any enemy fighting a Plagubearer must deduct -1 from all of its to hit rolls.
Magic: A unit of Plaguebearers has a magic level and can cast spells like a wizard. The size of the unit defines its magic level and the number of spells it has. 1-5 models = magic level 1 / 1 spell. 6-10 models = magic level 2 / 2 spell. 11-15 models = magic level 3/ 3 spell. 16+ models = magic level 4 / 4 spell.
Nurglings
Although they are tiny, there are a great many of them, and they move together in a writhing mass like a sea of green corruption. These are my favourites of the Daemons, cheap screens that cause fear and have three Wounds and three Attacks, and you don't have to summon them.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Nurglings have a Daemonic save of 4+ on a d6.
Fear: Nurglings cause fear as described in the Warhammer 40,000 rulebook.
Lord of Change
The Lord of Change is the wisest and the most subtle of all the Greater Daemons. His gaze penetrates to the very depths of the soul, exposing the victim's innermost hopesand fears. The Daemon is huge, with the plumage of a bird, and vast multi-coloured wings, the head of a monstrous predatory bird, with scaled legs bearing sharp and deadly talons.
Special Rules
Greater Daemon: All the special rules for Daemons apply as described in the Chaos Daemon section of Codex: Chaos.
Terror: Lords of Change cause Terror as per the terror rules in the psychology section of the Warhammer 40,000 rulebook. Remember that creatures that cause terror also cause fear.
Fly: The Lord of Change has wings and can fly as described in the Warhammer 40,000 rulebook.
Magic: The Lord of Change is a sorcerer with a magic level of 4, and may draw four spells from the Tzeentch deck.
Discs of Tzeentch
They take the shape of flattened, plate-like creatures, with viscious teeth and sharp spines. A Champion of Tzeentch can ride a Disc into battle.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Discs have a Daemonic save of 4+ on a d6.
Fly: Discs can fly as described in the Warhammer 40,000 rulebook.
Fear: Discs cause fear as described in the Warhammer 40,000 rulebook.
Flamers of Tzeentch
Flamers are strange in appearance, appearing to be an inverted mushroom with two flexible arms that each spit magical flames. It moves by jumping and bounding.
Special Rules
Daemons: All of the special rules for Daemons apply as described in Codex: Chaos. Flamers have a Daemonic save of 4+ on a d6.
Fear: Flamers cause fear as described in the Warhammer 40,000 rulebook.
Shoot Flame: The magical flame has a range of 6". No deductions made for long range and any target struck takes d6 S3 hits.
Bound: Flamers move by bounding. They can move over any obstacle without penalty. See the movement section in the Warhammer 40,000 rulebook.
Flame Attacks: Flamers also use their flames to engulf and detroy any opponents in close combat. Any model that suffers a wound takes d3 wound instead of one.
Horrors of Tzeentch
There are two types of Horrors, they all begin as Pink Horrors. When a Pink Horror is wounded, it emits a piercing squeal and immediately splits into two Blue Horrors. Both types fight together in a blur of blue and pink radiance.
Special Rules
Daemons: All of the special rules for Daemons apply, but Horrors do not receive the usual savings throw for Daemons.
Fear: Horrors cause fear as described in the Warhammer 40,000 rulebook.
Split: When a Pink Horror sustains a wound, it does not die, but instead splits into two Blue Horrors. Remove the model and replace it with two Blue Horror models. Unlike other Daemons, neither Horror receives a Daemon savings throw.
Magic: A unit of Pink Horrors has a magic level and can cast spells like a wizard. The size of the unit defines its magic level and the number of spells it has. 1-5 models = magic level 1 / 1 spell. 6-10 models = magic level 2 / 2 spell. 11-15 models = magic level 3/ 3 spell. 16+ models = magic level 4 / 4 spell. Note that Blue Horrors do not count. Spells must be drawn from the Tzeentch spell deck.