Damage is any means by which a unit's (i.e. the player, NPC, or a monster) current health can be reduced.
All forms of damage in Crypt of the NecroDancer are classified by damage types. There are 3 damage types: Normal, Piercing and Phasing.
Normal Damage[]
Normal Damage is the most common type of damage in the game. It is the damage type of attacks of all monsters, traps, spells, bombs, special equipment (Holy Water, Boots of Pain, Boots of Lunging and Infernal Torch) and almost all weapons. It doesn't have any specific traits.
Piercing Damage[]
Piercing Damage is able to damage certain enemies through their defense (e.g. Armored Skeletons' shields).
Piercing does its damage through the defense of the following monsters:
Armadillos
Armored Skeletons- Beetles
- Skeleton Knights
- Blademasters
- Gargoyles
- Death Metal
- Devils
- Orcs
The sources of Piercing Damage are:
- Crossbows (when loaded)
- Blunderbuss (when loaded)
- Rifle (when loaded)
- Dagger of Frost
- Ring of Piercing
- Rat Familiar
- Throwing Stars
- Daggers, Spears and Glass Shards (when thrown)
Phasing Damage[]
Phasing Damage can damage all enemies without any restrictions. It can, for example, damage Fake Walls without retreating or damage Wights inside of walls.
Phasing is able to do everything that piercing damage can do, and can damage monsters even in their invulnerable state. The following are the notable effects of Phasing Damage:
- Ghosts can be damaged even when facing them.
- Chest Mimics can be damaged even on the next beat after becoming active.
- Moles can be damaged even when they are burrowed.
- Tar Monsters can be damaged even on the next beat after becoming active.
- Wights, Ghasts, and Ghouls can be damaged even when they are inside walls, skipping their teleport moves.
- Fake Walls can be damaged even on the next beat after becoming active.
- Cauldron Mimics can be damaged even on the next beat after becoming active.
- Coral Riff's head can be damaged even during the first phase.
- Spiders can be damaged even when on walls.
- King Conga can be damaged even when he's on his throne.
- Dead Ringer can be damaged directly, for only 1 heart on each hit.
- Electric Zombies can be damaged even when they're charged.
- Lightning Orbs created by Lightning Mages can be damaged.
- Skeletons are included in the damage done to the attacked Skull.
- Petrified Gorgons can be damaged.
- Crate, Barrel, and Shrine Mimics can be damaged even on the next beat after becoming active.
- Fortissimole can be damaged even when he's burrowed or on stage platforms.
- Frankensteinway's shield generators can be damaged.
The sources of Phasing Damage are:
- Dagger of Phasing.
- Spell of Earth, if an affected monster is blocked from being knocked back.
Piercing and Phasing attacks will not knock armored enemies, except for Armadillos, Skeleton Knights, and Devils; or unless the player is wearing a 
Ring of War.