diff --git a/db/re/skill_db.yml b/db/re/skill_db.yml
index a59998bcc9..4e37fb410b 100644
--- a/db/re/skill_db.yml
+++ b/db/re/skill_db.yml
@@ -7235,6 +7235,7 @@ Body:
     TargetType: Self
     DamageFlags:
       IgnoreDefense: true
+      SimpleDefense: true
     Range: 9
     Hit: Single
     HitCount: 1
@@ -7664,6 +7665,7 @@ Body:
     TargetType: Attack
     DamageFlags:
       IgnoreFlee: true
+      SimpleDefense: true
     Flags:
       TargetTrap: true
     Range: -2
@@ -9452,6 +9454,7 @@ Body:
     DamageFlags:
       IgnoreAtkCard: true
       IgnoreFlee: true
+      SimpleDefense: true
     Flags:
       IsNpc: true
       TargetSelf: true
@@ -19110,6 +19113,7 @@ Body:
     DamageFlags:
       Splash: true
       IgnoreFlee: true
+      SimpleDefense: true
     Flags:
       TargetTrap: true
     Range: 9
@@ -22655,6 +22659,7 @@ Body:
     DamageFlags:
       Splash: true
       IgnoreFlee: true
+      SimpleDefense: true
     Flags:
       AllowOnMado: true
     Range: 9
@@ -28789,6 +28794,7 @@ Body:
     DamageFlags:
       Splash: true
       IgnoreFlee: true
+      SimpleDefense: true
     Range:
       - Level: 1
         Size: 7
@@ -33145,6 +33151,7 @@ Body:
     DamageFlags:
       Splash: true
       IgnoreFlee: true
+      SimpleDefense: true
     Flags:
       TargetTrap: true
     Range: 9
diff --git a/doc/skill_db.txt b/doc/skill_db.txt
index 6b6461b975..265fe9a3d4 100644
--- a/doc/skill_db.txt
+++ b/doc/skill_db.txt
@@ -58,6 +58,7 @@ IgnoreFlee		- Skill ignores target's flee (Magic type always ignores)
 IgnoreDefCard	- Skill ignores target's defense cards.
 IgnoreLongCard	- Skill ignores caster's long range damage cards.
 Critical		- Skill can critical.
+SimpleDefense	- (Renewal-only) Physical damage is flatly reduced by DEF+DEF2. RES is ignored.
 
 ---------------------------------------
 
diff --git a/src/map/battle.cpp b/src/map/battle.cpp
index 2682071ffc..d87fdb8990 100644
--- a/src/map/battle.cpp
+++ b/src/map/battle.cpp
@@ -6648,42 +6648,31 @@ static void battle_calc_defense_reduction(struct Damage* wd, struct block_list *
 	}
 
 #ifdef RENEWAL
-	switch(skill_id) {
-		case RK_DRAGONBREATH:
-		case RK_DRAGONBREATH_WATER:
-		case NC_ARMSCANNON:
-		case GN_CARTCANNON:
-		case MO_EXTREMITYFIST:
-			if (attack_ignores_def(wd, src, target, skill_id, skill_lv, EQI_HAND_R) || attack_ignores_def(wd, src, target, skill_id, skill_lv, EQI_HAND_L))
-				return;
-			if (is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_R) || is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_L))
-				return;
-			[[fallthrough]];
-		case CR_GRANDCROSS: // Grand Cross is marked as "IgnoreDefense" in renewal as it's applied at the end after already combining ATK and MATK
-		case NPC_GRANDDARKNESS:
-			// Defense reduction by flat value.
-			// This completely bypasses the normal RE DEF Reduction formula.
-			wd->damage -= (def1 + vit_def);
-			if (is_attack_left_handed(src, skill_id))
-				wd->damage2 -= (def1 + vit_def);
-			break;
+	std::bitset<NK_MAX> nk = battle_skill_get_damage_properties(skill_id, wd->miscflag);
+
+	if (nk[NK_SIMPLEDEFENSE]) {
+		// Defense reduction by flat value.
+		// This completely bypasses the normal RE DEF Reduction formula.
+		wd->damage -= (def1 + vit_def);
+		if (is_attack_left_handed(src, skill_id))
+			wd->damage2 -= (def1 + vit_def);
+	}
+	else {
 		/**
 		 * RE DEF Reduction
 		 * Damage = Attack * (4000+eDEF)/(4000+eDEF*10) - sDEF
 		 * Pierce defence gains 1 atk per def/2
 		 */
-		default:
-			if( def1 == -400 ) /* -400 creates a division by 0 and subsequently crashes */
-				def1 = -399;
-			ATK_ADD2(wd->damage, wd->damage2,
-				is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_R) ? (def1*battle_calc_attack_skill_ratio(wd, src, target, skill_id, skill_lv))/200 : 0,
-				is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_L) ? (def1*battle_calc_attack_skill_ratio(wd, src, target, skill_id, skill_lv))/200 : 0
-			);
-			if( !attack_ignores_def(wd, src, target, skill_id, skill_lv, EQI_HAND_R) && !is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_R) )
-				wd->damage = wd->damage * (4000+def1) / (4000+10*def1) - vit_def;
-			if( is_attack_left_handed(src, skill_id) && !attack_ignores_def(wd, src, target, skill_id, skill_lv, EQI_HAND_L) && !is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_L) )
-				wd->damage2 = wd->damage2 * (4000+def1) / (4000+10*def1) - vit_def;
-			break;
+		if (def1 == -400) /* -400 creates a division by 0 and subsequently crashes */
+			def1 = -399;
+		ATK_ADD2(wd->damage, wd->damage2,
+			is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_R) ? (def1 * battle_calc_attack_skill_ratio(wd, src, target, skill_id, skill_lv)) / 200 : 0,
+			is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_L) ? (def1 * battle_calc_attack_skill_ratio(wd, src, target, skill_id, skill_lv)) / 200 : 0
+		);
+		if (!attack_ignores_def(wd, src, target, skill_id, skill_lv, EQI_HAND_R) && !is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_R))
+			wd->damage = wd->damage * (4000 + def1) / (4000 + 10 * def1) - vit_def;
+		if (is_attack_left_handed(src, skill_id) && !attack_ignores_def(wd, src, target, skill_id, skill_lv, EQI_HAND_L) && !is_attack_piercing(wd, src, target, skill_id, skill_lv, EQI_HAND_L))
+			wd->damage2 = wd->damage2 * (4000 + def1) / (4000 + 10 * def1) - vit_def;
 	}
 #else
 		if (def1 > 100) def1 = 100;
@@ -7507,10 +7496,9 @@ static struct Damage battle_calc_weapon_attack(struct block_list *src, struct bl
 
 		// Res reduces physical damage by a percentage and
 		// is calculated before DEF and other reductions.
-		// TODO: It seems all skills that use the simple defense formula (damage substracted by DEF+DEF2) ignore Res
-		// TODO: We should add a flag for those skills or use the IgnoreDefense flag after confirming all
+		// All skills that use the simple defense formula (damage substracted by DEF+DEF2) ignore Res
 		// TODO: Res formula probably should be: (2000+x)/(2000+5x), but with the reduction rounded down
-		if ((wd.damage + wd.damage2) && tstatus->res > 0 && skill_id != MO_EXTREMITYFIST && skill_id != GN_CARTCANNON && skill_id != NC_ARMSCANNON) {
+		if ((wd.damage + wd.damage2) && tstatus->res > 0 && !nk[NK_SIMPLEDEFENSE]) {
 			short res = tstatus->res;
 			short ignore_res = 0;// Value used as a percentage.
 
@@ -8786,7 +8774,6 @@ struct Damage battle_calc_magic_attack(struct block_list *src,struct block_list
 #ifdef RENEWAL
 		// MRes reduces magical damage by a percentage and
 		// is calculated before MDEF and other reductions.
-		// TODO: Check if there are skills that ignore Mres, similar to skills that ignore Res
 		// TODO: MRes formula probably should be: (2000+x)/(2000+5x), but with the reduction rounded down
 		if (ad.damage && tstatus->mres > 0) {
 			short mres = tstatus->mres;
diff --git a/src/map/script_constants.hpp b/src/map/script_constants.hpp
index 6a111ebcfe..1e459f6e6f 100644
--- a/src/map/script_constants.hpp
+++ b/src/map/script_constants.hpp
@@ -10654,6 +10654,7 @@
 	export_constant(NK_IGNOREDEFCARD);
 	export_constant(NK_IGNORELONGCARD);
 	export_constant(NK_CRITICAL);
+	export_constant(NK_SIMPLEDEFENSE);
 
 	/* skill inf */
 	export_constant(INF_PASSIVE_SKILL);
diff --git a/src/map/skill.hpp b/src/map/skill.hpp
index e485ce8b12..5956955adf 100644
--- a/src/map/skill.hpp
+++ b/src/map/skill.hpp
@@ -58,6 +58,7 @@ enum e_skill_nk : uint8 {
 	NK_IGNOREDEFCARD,
 	NK_CRITICAL,
 	NK_IGNORELONGCARD,
+	NK_SIMPLEDEFENSE,
 	NK_MAX,
 };