Protection is a defensive attribute that serves as damage reduction. While Defence Skill prevents attacks from hitting, and while Hit Points prevent attacks from killing, Protection reduces the HP impact of most attacks that get through Defence Skill.

Combat in Dominions is similar to that in Fire Emblem and other tactical RPGs, with Defence Skill being Evasion, Protection being Defense, and HP being what it always is. Alternatively, if this were a spaceship game, HP would be Hull, Protection would be Armor, and Defence Skill would be a cross between Evasion and Energy Shields.

When a hit lands, it gets a Damage DRN roll, and the target gets a Protection DRN roll. For melee hits, the base for the Damage roll is derived from the weapon strength and the user's Strength. This is also true for most close-range missile hits (those from thrown weapons), but long-ranged missile hits typically rely on Strength a lot less.

In the most-basic case, the base of the target's Protection roll is their Protection score for the area being hit, and the resulting difference between the two rolls is the base damage dealt. In Dominions 6, the Torso, the Arms, and the Legs are all covered by Body Protection, while the Head is only covered by Head Protection. Only Area-of-Effect (AOE) attacks such as Gifts from Heaven hit the target's Average Protection (the score shown on the main character sheet), which is calculated by adding 90% of Body Protection with 10% of Head Protection.

Dominions does have critical hits, but these are more akin to critical failures on the part of the target. If the DRN on the Protection roll (two d6's, with rolled 6's being counted as 5's and prompting another roll) yields a 2, the Protection added to that roll is reduced by 25%. This is multiplicative. Fatigue on the target increases the threshold:

• 50 to 99 Fatigue makes the threshold 3, increasing the odds of an armor-defeating hit from 1/36 to 1/12.
• 100 or more Fatigue makes the threshold 4, increasing the odds of an armor-defeating hit to 1/6.
  • Immobility (either as a trait or as a byproduct of a temporary trait) also makes the threshold 4.

Very few attacks are utterly basic. Most nonmagical attacks have at least one sort of damage type, and a significant amount of magical attacks are either Armor-Piercing or Armor-Negating. An Armor-Piercing hit deducts 50% of the target's Protection from what's applied to their Protection roll, and an Armor-Negating hit has none of it apply.

• Piercing hits strike a fine point, deducting 15% from the target's Protection that's applied to their Protection roll. This is subtractive, so an Armor-Piercing Piercing hit (such as a Crossbow bolt) goes against only 35% of the target's Protection.
• Blunt hits are concussive, making them 25% stronger when hitting the Head. This is multiplicative, and it's applied after the Damage roll but before the Protection roll. The chance to hit a humanoid's Head varies with size and reach, but it's normally 10%.
• Slashing hits cut flesh and thus harm a wider area of the body, making them 25% stronger after both the Damage roll and the Protection roll are applied. This is also multiplicative.

Note that only one of these is applied on a hit, at random if the attack has more than one. A Short Sword can be used to either stab or slash, for instance, while Flying Shards may hit you with either a flat end or a sharp end.

There are three Protection scores: Natural Protection (which applies to both the Body and the Head), Armor Protection (which applies to whichever area it's worn on), and Shield Protection (which only applies if the Attack-versus-Defence rolls resulted in a shield hit).

Natural Protection and Armor Protection stack, but with diminishing returns. They cannot add up to be greater than 40, though a unit with zero Natural Protection or zero Armor Protection could technically have more than 40 in the other. This is enforced by a penalty equal to the two multiplied together and divided by 40, though the result is rounded up.

For example, say a unit with 4 Natural Protection wears armor that provides 15 Protection to the body.
Their Body Protection is [15 + 4 - (15 * 4 / 40)], simplified down to 19 - 1.5, or 17.5. This is rounded up to 18.

Shield Protection is added on without diminishing returns.

A shield can be partially overwhelmed. Shields can be damaged by a hit whose damage before the Protection roll is triple the shield's Protection score, plus 15 if the shield is magical; as a result, the shield's Protection is reduced by 20% before the Protection roll is performed, and it remains that way for the rest of the battle. If it's 5x the shield's Protection (plus 25 if the shield is magical), the shield is broken, and the penalty is 50%.

The above penalties do not stack, neither with themselves nor with each other; however, a damaged shield that is damaged again has a 25% chance to be broken.

Blunt hits count as being 25% stronger for damaging/breaking shields, while Slashing hits count as being 50% stronger.

The Protection penalties are the same for damaged/broken Armor, if it somehow gets damaged or broken. Armor damage most-commonly happens to rusty armor; the chance for damage to rusty armor is calculated by taking the Damage roll, subtracting Shield Protection if the hit was a shield hit, and multiplying it by 2%. In Dominions, ordinary hits otherwise don't damage armor.