Enemy Type

Enemies in Darkest Dungeon belong to certain classes. They can normally be ignored, however some quirks will cause characters to fear certain enemies because of their class. However there are also certain quirk that grant bonus against these classes, as well as certain skills and trinkets. An enemy can have up to two classes

Human
Humans are mortal creatures that either conspire with the darkness or stand against you for their own selfish gains. They have no built-in resistances and are quick to fall, however their skills are versatile and form the backbone of many teams. From hero's lowering resistances, multi-target attacks, causing stress and even marking their foes so other vile monstrosities can finish weakened prey off, human enemies should not be underestimated and be dealt with swiftly.

Humans are most often found within the Weald and the swinefolk of the Warrens are half human. That said they are the most common class and can be found just about anywhere. The Bounty Hunter's Collect Bounty does bonus damage against humans, and some Trinkets give heroes bonus damage against humans.

Beast
Beast are savage animals that have been tainted by the spreading darkness or awakened by those who trespass into their ancient domain. Almost every beast will assault you with a form of sickness waiting to spread itself to your heroes. Beasts will assault you with bleed, blight, disease and even lowering your immunity to disease. Many of them will also cause stress while trying to infest you with their maladies, such as the Swine Wretch and Carrion Eater.

It should come as no surprise, then, that many beasts make their homes within the sewers of the Warrens and the poisonous groves of the Weald. Because of the sickness has infested them for so long, they are unlikely to be harmed by it themselves, so one should think before attempting to use blight within these areas. The Hound Master's Hound's Rush does extra damage to beasts, and some Trinkets give a hero bonus damage against beasts.

Unholy
Twisted creatures that stand against all that is good, Unholy enemies can be encountered in any dungeon but they are particularly rife in the Ruins where the Necromancer raises them without end. Unholy creatures commonly have a high enough resistance to bleed that they are virtually immune, however the corrosion that blight provides will decay their abominable bodies back into the dust. Ghouls are a notable unholy enemy that can bleed, however it's also one of the most dangerous creatures you will find outside of bosses and should not be taken lightly. The Crusader and the Vestal both use attacks that do bonus damage to Unholy creatures, and some Trinkets give heroes bonus damage against unholy.

Eldritch
By all rights these creatures should not exist. At best they are alien, and at worst they are a terrible reminder of how easily even the toughest minds can be torn down. Normally they are entirely restricted to the Weald, the Cove, and the Darkest Dungeon. However, who knows when their madness will come crawling out of the darkness to sink their tendrils into an unsuspecting party.

The resistances of these creatures vary depending on where you find them. For example the eldritch found in the Weald are resistant to blight but weak to bleed, but the fish-headed abominations of the cove have extra resistance to bleed from their scaly skin, but have weak resistance against blight. Many of the Occultist's attacks do bonus damage to eldritch monsters, and some Trinkets give heroes bonus damage against Eldritch.

Other types
A few other types exist. These enemies are all inanimate objects found only in certain boss battles, in which skills or trinkets have no bonus damage against them. They are as follows:
 * CARPENTRY is the type of the Pews that the Prophet uses to defend himself and the Barrel O' Bombs that the brigand leader Vvulf takes with him to destroy and ravage.
 * CROCKERY is the type of the Cauldron the Hag uses in her potion brewing.
 * IRONWORK is the type of the Brigand Pounder.
 * COSMIC is the type of the Final Boss (Spoilers here.)

Trivia
Eldritch is the most popular type, with 38 enemies having that type. Not counting miscellaneous types, Unholy is the least popular with a mere 15 enemies.