There are seven types of damage in Royal Revolt 2.
This basic damage type is only dealt by the Hero, the Knight, the Werewolf and the Monk. The only unit that is especially affected by it is the Paladin, which is weak to normal damage. The spell Bladestorm also deals normal damage which greatly affects Barricades and Blockades, even though they otherwise are not particularly vulnerable to normal damage.
Weapons and gauntlets always deal normal damage as their primary damage type, but can additionally deal another type of damage as well.
There are some items which can protect the hero from normal damage. However, since only few units deal this type of damage to the hero, the usefulness of such a protection is questionable.
Blunt damage is dealt by Paladins, Cannons, Gargoyles, Bomb Towers and Skull Towers as well. Strikes from the Ogre also deal blunt damage over a small area of effect (AoE damage). Spells that deal blunt damage include Hammerstrike and Sonic Blast.
All structures are vulnerable to blunt damage, which makes Paladins and especially Cannons a great addition to any offensive strategies. Paladins, Frosters, Cannons, and Ogres have some resistance against this damage type.
Some weapons and gauntlets have blunt damage as a secondary attribute. There are no protective items against blunt damage.
Structures generally have a 50% to 75% resistance against piercing damage. Paladins are especially protected from piercing damage as well.
Only Festival belt Yeren have piercing damage as an attribute.
Only Festival pauldron Nuk-luk have piercing resistance as an attribute.
Frosters, Frost towers, Frenzy Frost Blasters, and the Blizzard spell deal ice damage. While the damage itself is often negligible, ice damage slows affected units and towers down, hindering their movement and reducing their attack speed for a while.
Except for the Blizzard spell, ice damage usually comes in small amounts. However, the amount of damage is secondary to the slowing effect. Multiple sources of ice damage, like several Frosters, can increase the amount of damage, but won’t enhance the slowing effect. This is why one Froster or Frost Tower is usually sufficient.
With ice damage coming in small doses anyway, weaknesses or protection against this damage type are usually irrelevant.
The hero can benefit from the slowing effect through gauntlets and weapons with ice damage as well. This can be especially helpful against towers since one hit will slow their firing speed down considerably.
There is also protective gear available to reduce the ice damage dealt to the hero. This will, however, not protect the hero from the slowing effect. Since ice damage against the hero usually only comes in negligible quantities, such gear is a questionable investment.
Fire damage is dealt by Pyromancers, Firebolt Towers, and the Firestorm spell. Being hit by fire causes units and structures to burn and take additional damage for a while. In case of the Firestorm spell, the burning only continues for the remainder of the spell.
Upon being lit on fire, some units have a chance to panic. While panicking, they will run around mindlessly for a few seconds.
Fire is especially harmful to wooden structures like arrow towers and barricades. Firebolt Towers are also extremely weak against fire damage. Frosters, Cannons, and Mortars are very vulnerable as well.
There are some weapons and gauntlets with secondary fire damage available for the hero. There’s also protective gear against fire, which can be very helpful against Pyromancers (mid game) or Firebolt Towers (late game).
Mortars, Mummies, Snake Towers and the Toxic Cloud spell deal poison damage. Poison lingers a while, dealing damage for a few additional seconds. In case of the Toxic Cloud spell, this continues for the remainder of the spell.
Poison is especially harmful to Paladins, making Toxic Cloud a recommended choice against defenses that rely heavily on Paladin waves. Later, Mortars can be used to combat Paladins as well as Arblasters, which are also vulnerable to poison.
Structures are virtually unaffected by poison.
For the Hero there are some poisoned weapons and gauntlets as well as protective gear against poison available.
Lightning damage is dealt only by Lightning Tower. It's very powerful against any type of units and hero, too, especially if the tower is boosted as Tempest Tower. The only way to feel less damage is by using Shield or by healing the units or the hero after its attack.
The fact that there is no protection for the hero's equipment makes lightning damage a valid reason to place Lightning Towers in your base.