Champions and Rares are monsters with blue or yellow names, any normal monster can spawn as one. They are much more powerful than regular monsters and travel in groups. They have the possibility of dropping the best items in the game. In addition they have abilities called affixes, which grant special them special properties such as being able to create walls out of thin air or even make clones of themselves. The affixes that can spawn on a monster are completely random.
At level 60 every Champion or Elite you kill will grant you a spell buff called "Nephalem Valor" but that is a topic for another guide.
Some combinations of Champions and Rares can be fairly easy, but don't let that fool you some combinations are absolutely deadly such as a Mortar, Fire chains and Molten pack. This guide goes over every possible affix.
This ability pulls the player to the monster that casted the spell, but causes no damage. A monster requires line of sight to see you, meaning they can not pull you from behind walls or around corners. By itself vortex is not particular dangerous for a melee as they are already up next to the monster, but combined with other affixes such as Arcane Enchanted, Molten, Desecrator - getting pulled into any of those can be certain death.
This affix is only possible on Champion monsters and only if more than one is alive. Health Link gives all the champions one large health pool, and the damage you deal to one applies to all of them as long as they are nearby.
Jailer gives monsters the ability to trap a player in a prison for a few seconds. Like Vortex, this is not dangerous by itself, but being jailed while a beam of arcane comes towards you is a heart pounding moment. Jailer is worst for any class or player that kills by kiting, being stopped dead in your tracks makes getting away tough. Luckily a few classes have skills to deal with Jailer, for example monks can use Dashing strike to move but it does not free Here is a quick list of all skills that can free you from Jailer
This affix gives a monster the ability to summon a deadly force of arcane magic, a small circle is placed on the ground and a few seconds later a beam shoots out of from it traveling in a random circular direction. Do not get caught in this! It is one of the most deadly affixes.
Any monster with this affix has extra health, making even weaker packs of Champions/Elites take a while to kill.
Only rare monsters can have this affix. It increases the amount of minions a monster has by 2-3x
Only Champion monsters can spawn with the Avenger affix. When a monster that belongs to a Champion group with the Avenger affix dies, the rest of the pack gains in size and strength. This can make an already difficulty pack even harder as each monster dies.
Desecrator is a targeted spell that creates an area of death on the ground. It takes 1 second for a newly formed Desecrator circle to begin doing damage, get out of these as quick as you can.
Lighting shoots out at every direction whenever the monster attacks, or is attacked.
Everytime you hit a Champion or Rare with the Reflect Damage affix you take a portion of the damage you dealt back at yourself.
Every thing the monster does is done much quicker.
While a molten monster moves it leaves behind a trail of lava that does considerable damage to anyone standing in it. When a molten monster dies it leaves behind a bomb that explodes after a few seconds dealing a large amount of damage to anyone nearby
Only champions can spawn with this Fire Chains affix, it creates a chain of fire between itself and the other champion monsters in its pack. If you happen to get caught between two monsters, expect to take a lot of damage. Monster AI is also changed to try and trap the player between the chains.
Allows a monster to teleport at will, away from battle or into battle.
Frozen monsters do cold damage with every attack, they also possess the ability to summon frozen balls that over a few seconds explode freezing any player caught in its radius.
Illusionist allows a monster to create clones of it self that are much weaker and have less total health, they do however spawn with the same percent of health as the monster they were cloned from.
Every hit from a Knockback monster has a chance to knock back the player and slow them for a few seconds
Waller allows monsters to create walls out of thin air, these walls can trap a player allowing them not to run away. A lot of spells can not pass through Waller either, providing the monster a moment of protection.
A faint circle in a large area appears around the monster, any projectile that enters the sphere is slowed considerable. It is very similar to the Wizard Spell, Slow Time.
Mortar allows a monster to hurl firebombs at the player, they only hit players out of melee range but if they do hit you, they do a considerable amount of damage.
Nightmare has a chance to be inflicted on a player everytime they are hit by a monster imbued with the Nightmarish ability, they will flee from battle for a seconds while they player is unable to control the character.
A percent of damage the monster causes to you, heals the monster.
Plagued monsters leave a large area of poison on the ground that deals damage to any player standing on it, unlike Desecrator and Molten, Plagued does not disappear until the monster that casted it dies.
The monster creates a shield around itself making itself invincible to all forms of damage for a few seconds.