diff --git a/include/extern.h b/include/extern.h
index 3fd48ac1d..6fa48fd2e 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1495,6 +1495,7 @@ extern struct attack *attacktype_fordmg(struct permonst *, int, int);
 extern boolean attacktype(struct permonst *, int);
 extern boolean noattacks(struct permonst *);
 extern boolean poly_when_stoned(struct permonst *);
+extern boolean defended(struct monst *, int);
 extern boolean resists_drli(struct monst *);
 extern boolean resists_magm(struct monst *);
 extern boolean resists_blnd(struct monst *);
diff --git a/src/artifact.c b/src/artifact.c
index 3458f1855..d94487642 100644
--- a/src/artifact.c
+++ b/src/artifact.c
@@ -384,7 +384,7 @@ restrict_name(struct obj *otmp, const char *name)
 static boolean
 attacks(int adtyp, struct obj *otmp)
 {
-    register const struct artifact *weap;
+    const struct artifact *weap;
 
     if ((weap = get_artifact(otmp)) != 0)
         return (boolean) (weap->attk.adtyp == adtyp);
@@ -394,10 +394,48 @@ attacks(int adtyp, struct obj *otmp)
 boolean
 defends(int adtyp, struct obj *otmp)
 {
-    register const struct artifact *weap;
+    struct artifact *weap;
 
     if ((weap = get_artifact(otmp)) != 0)
         return (boolean) (weap->defn.adtyp == adtyp);
+    if (Is_dragon_armor(otmp)) {
+        int otyp = otmp->otyp;
+
+        /* convert mail to scales to simplify testing */
+        if (Is_dragon_mail(otmp))
+            otyp += GRAY_DRAGON_SCALES - GRAY_DRAGON_SCALE_MAIL;
+
+        switch (adtyp) {
+        case AD_MAGM: /* magic missiles => general magic resistance */
+            return (otyp == GRAY_DRAGON_SCALES);
+        case AD_HALU: /* confers hallucination resistance */
+            return (otyp == GOLD_DRAGON_SCALES);
+        case AD_FIRE:
+      /*case AD_BLND: -- gives infravision but does not prevent blindness */
+            return (otyp == RED_DRAGON_SCALES); /* red but not gold */
+        case AD_COLD:
+      /*case AD_FAMN: -- slows digestion but does not override Famine */
+            return (otyp == WHITE_DRAGON_SCALES); /* white but not silver */
+        case AD_DRST: /* drain strength => poison */
+        case AD_DISE: /* blocks disease but not slime */
+            return (otyp == GREEN_DRAGON_SCALES);
+        case AD_SLEE: /* sleep */
+        case AD_PLYS: /* paralysis => free action */
+            return (otyp == ORANGE_DRAGON_SCALES);
+        case AD_DISN: /* disintegration */
+        case AD_DRLI: /* level drain resistance */
+            return (otyp == BLACK_DRAGON_SCALES);
+        case AD_ELEC: /* electricity == lightning */
+        case AD_SLOW: /* confers speed so blocks speed removal */
+            return (otyp == BLUE_DRAGON_SCALES);
+        case AD_ACID:
+        case AD_STON: /* petrification resistance */
+            return (otyp == YELLOW_DRAGON_SCALES);
+        default:
+            /* SILVER_DRAGON_SCALES don't resist any particular attack type */
+            break;
+        }
+    }
     return FALSE;
 }
 
@@ -405,7 +443,7 @@ defends(int adtyp, struct obj *otmp)
 boolean
 defends_when_carried(int adtyp, struct obj *otmp)
 {
-    register const struct artifact *weap;
+    const struct artifact *weap;
 
     if ((weap = get_artifact(otmp)) != 0)
         return (boolean) (weap->cary.adtyp == adtyp);
@@ -739,11 +777,9 @@ spec_applies(const struct artifact *weap, struct monst *mtmp)
                      : (ptr->maligntyp == A_NONE
                         || sgn(ptr->maligntyp) != weap->alignment);
     } else if (weap->spfx & SPFX_ATTK) {
-        struct obj *defending_weapon = (yours ? uwep : MON_WEP(mtmp));
-
-        if (defending_weapon && defending_weapon->oartifact
-            && defends((int) weap->attk.adtyp, defending_weapon))
+        if (defended(mtmp, (int) weap->attk.adtyp))
             return FALSE;
+
         switch (weap->attk.adtyp) {
         case AD_FIRE:
             return !(yours ? Fire_resistance : resists_fire(mtmp));
diff --git a/src/mhitm.c b/src/mhitm.c
index 234515594..e3bf647b6 100644
--- a/src/mhitm.c
+++ b/src/mhitm.c
@@ -1064,7 +1064,7 @@ paralyze_monst(struct monst *mon, int amt)
 int
 sleep_monst(struct monst *mon, int amt, int how)
 {
-    if (resists_sleep(mon)
+    if (resists_sleep(mon) || defended(mon, AD_SLEE)
         || (how >= 0 && resist(mon, (char) how, 0, NOTELL))) {
         shieldeff(mon->mx, mon->my);
     } else if (mon->mcanmove) {
diff --git a/src/mhitu.c b/src/mhitu.c
index c4446ba9d..99adda4a2 100644
--- a/src/mhitu.c
+++ b/src/mhitu.c
@@ -1392,7 +1392,7 @@ explmu(struct monst *mtmp, struct attack *mattk, boolean ufound)
         return MM_MISS;
 
     tmp = d((int) mattk->damn, (int) mattk->damd);
-    not_affected = defends((int) mattk->adtyp, uwep);
+    not_affected = defended(mtmp, (int) mattk->adtyp);
 
     if (!ufound) {
         pline("%s explodes at a spot in %s!",
@@ -1642,7 +1642,7 @@ gazemu(struct monst *mtmp, struct attack *mattk)
         break;
     case AD_SLOW:
         if (canseemon(mtmp) && couldsee(mtmp->mx, mtmp->my) && mtmp->mcansee
-            && (HFast & (INTRINSIC | TIMEOUT)) && !defends(AD_SLOW, uwep)
+            && (HFast & (INTRINSIC | TIMEOUT)) && !defended(mtmp, AD_SLOW)
             && !rn2(4)) {
             if (cancelled) {
                 react = 7; /* "dulled" */
diff --git a/src/mondata.c b/src/mondata.c
index 8e11b89c1..a45e7b871 100644
--- a/src/mondata.c
+++ b/src/mondata.c
@@ -76,7 +76,7 @@ noattacks(struct permonst* ptr)
 
 /* does monster-type transform into something else when petrified? */
 boolean
-poly_when_stoned(struct permonst* ptr)
+poly_when_stoned(struct permonst *ptr)
 {
     /* non-stone golems turn into stone golems unless latter is genocided */
     return (boolean) (is_golem(ptr) && ptr != &mons[PM_STONE_GOLEM]
@@ -84,20 +84,56 @@ poly_when_stoned(struct permonst* ptr)
     /* allow G_EXTINCT */
 }
 
+/* is 'mon' (possibly youmonst) protected against damage type 'adtype' via
+   wielded weapon or worn dragon scales? [or by virtue of being a dragon?] */
+boolean
+defended(struct monst *mon, int adtyp)
+{
+    struct obj *o, otemp;
+    int mndx;
+    boolean is_you = (mon == &g.youmonst);
+
+    /* is 'mon' wielding an artifact that protects against 'adtyp'? */
+    o = is_you ? uwep : MON_WEP(mon);
+    if (o && o->oartifact && defends(adtyp, o))
+        return TRUE;
+
+    /* if 'mon' is an adult dragon, treat it as if it was wearing scales
+       so that it has the same benefit as a hero wearing dragon scales */
+    mndx = monsndx(mon->data);
+    if (mndx >= PM_GRAY_DRAGON && mndx <= PM_YELLOW_DRAGON) {
+        /* a dragon is its own suit...  if mon is poly'd hero, we don't
+           care about embedded scales (uskin) because being a dragon with
+           embedded scales is no better than just being a dragon */
+        otemp = cg.zeroobj;
+        otemp.oclass = ARMOR_CLASS;
+        otemp.otyp = GRAY_DRAGON_SCALES + (mndx - PM_GRAY_DRAGON);
+        /* defends() and Is_dragon_armor() only care about otyp so ignore
+           the rest of otemp's fields */
+        o = &otemp;
+    } else {
+        /* ordinary case: not an adult dragon */
+        o = is_you ? uarm : which_armor(mon, W_ARM);
+    }
+    /* is 'mon' wearing dragon scales that protect against 'adtyp'? */
+    if (o && Is_dragon_armor(o) && defends(adtyp, o))
+        return TRUE;
+
+    return FALSE;
+}
+
 /* returns True if monster is drain-life resistant */
 boolean
-resists_drli(struct monst* mon)
+resists_drli(struct monst *mon)
 {
     struct permonst *ptr = mon->data;
-    struct obj *wep;
 
     if (is_undead(ptr) || is_demon(ptr) || is_were(ptr)
         /* is_were() doesn't handle hero in human form */
         || (mon == &g.youmonst && u.ulycn >= LOW_PM)
         || ptr == &mons[PM_DEATH] || is_vampshifter(mon))
         return TRUE;
-    wep = (mon == &g.youmonst) ? uwep : MON_WEP(mon);
-    return (boolean) (wep && wep->oartifact && defends(AD_DRLI, wep));
+    return defended(mon, AD_DRLI);
 }
 
 /* True if monster is magic-missile (actually, general magic) resistant */
diff --git a/src/uhitm.c b/src/uhitm.c
index 61ea2213a..8303c0090 100644
--- a/src/uhitm.c
+++ b/src/uhitm.c
@@ -1905,8 +1905,9 @@ mhitm_ad_dren(struct monst *magr, struct attack *mattk, struct monst *mdef,
 }
 
 void
-mhitm_ad_drli(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_drli(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     if (magr == &g.youmonst) {
         /* uhitm */
@@ -1914,7 +1915,8 @@ mhitm_ad_drli(struct monst *magr, struct attack *mattk, struct monst *mdef,
         /* since hero can't be cancelled, only defender's armor applies */
         boolean negated = !(rn2(10) >= 3 * armpro);
 
-        if (!negated && !rn2(3) && !resists_drli(mdef)) {
+        if (!negated && !rn2(3)
+            && !(resists_drli(mdef) || defended(mdef, AD_FIRE))) {
             mhm->damage = d(2, 6); /* Stormbringer uses monhp_per_lvl
                                     * (usually 1d8) */
             pline("%s becomes weaker!", Monnam(mdef));
@@ -1958,8 +1960,9 @@ mhitm_ad_drli(struct monst *magr, struct attack *mattk, struct monst *mdef,
         int armpro = magic_negation(mdef);
         boolean cancelled = magr->mcan || !(rn2(10) >= 3 * armpro);
 
-        if (!cancelled && !rn2(3) && !resists_drli(mdef)) {
-            mhm->damage = d(2, 6); /* Stormbringer uses monhp_per_lvl(usually 1d8) */
+        if (!cancelled && !rn2(3)
+            && !(resists_drli(mdef) || defended(mdef, AD_DRLI))) {
+            mhm->damage = d(2, 6); /* Stormbringer uses monhp_per_lvl (1d8) */
             if (g.vis && canspotmon(mdef))
                 pline("%s becomes weaker!", Monnam(mdef));
             if (mdef->mhpmax - mhm->damage > (int) mdef->m_lev) {
@@ -1982,8 +1985,9 @@ mhitm_ad_drli(struct monst *magr, struct attack *mattk, struct monst *mdef,
 }
 
 void
-mhitm_ad_fire(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_fire(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     struct permonst *pd = mdef->data;
 
@@ -2017,7 +2021,7 @@ mhitm_ad_fire(struct monst *magr, struct attack *mattk, struct monst *mdef,
         }
         mhm->damage += destroy_mitem(mdef, SCROLL_CLASS, AD_FIRE);
         mhm->damage += destroy_mitem(mdef, SPBOOK_CLASS, AD_FIRE);
-        if (resists_fire(mdef)) {
+        if (resists_fire(mdef) || defended(mdef, AD_FIRE)) {
             if (!Blind)
                 pline_The("fire doesn't heat %s!", mon_nam(mdef));
             golemeffects(mdef, AD_FIRE, mhm->damage);
@@ -2087,7 +2091,7 @@ mhitm_ad_fire(struct monst *magr, struct attack *mattk, struct monst *mdef,
         }
         mhm->damage += destroy_mitem(mdef, SCROLL_CLASS, AD_FIRE);
         mhm->damage += destroy_mitem(mdef, SPBOOK_CLASS, AD_FIRE);
-        if (resists_fire(mdef)) {
+        if (resists_fire(mdef) || defended(mdef, AD_FIRE)) {
             if (g.vis && canseemon(mdef))
                 pline_The("fire doesn't seem to burn %s!", mon_nam(mdef));
             shieldeff(mdef->mx, mdef->my);
@@ -2101,8 +2105,9 @@ mhitm_ad_fire(struct monst *magr, struct attack *mattk, struct monst *mdef,
 }
 
 void
-mhitm_ad_cold(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_cold(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     if (magr == &g.youmonst) {
         /* uhitm */
@@ -2116,7 +2121,7 @@ mhitm_ad_cold(struct monst *magr, struct attack *mattk, struct monst *mdef,
         }
         if (!Blind)
             pline("%s is covered in frost!", Monnam(mdef));
-        if (resists_cold(mdef)) {
+        if (resists_cold(mdef) || defended(mdef, AD_COLD)) {
             shieldeff(mdef->mx, mdef->my);
             if (!Blind)
                 pline_The("frost doesn't chill %s!", mon_nam(mdef));
@@ -2152,7 +2157,7 @@ mhitm_ad_cold(struct monst *magr, struct attack *mattk, struct monst *mdef,
         }
         if (g.vis && canseemon(mdef))
             pline("%s is covered in frost!", Monnam(mdef));
-        if (resists_cold(mdef)) {
+        if (resists_cold(mdef) || defended(mdef, AD_COLD)) {
             if (g.vis && canseemon(mdef))
                 pline_The("frost doesn't seem to chill %s!", mon_nam(mdef));
             shieldeff(mdef->mx, mdef->my);
@@ -2164,8 +2169,9 @@ mhitm_ad_cold(struct monst *magr, struct attack *mattk, struct monst *mdef,
 }
 
 void
-mhitm_ad_elec(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_elec(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     if (magr == &g.youmonst) {
         /* uhitm */
@@ -2180,7 +2186,7 @@ mhitm_ad_elec(struct monst *magr, struct attack *mattk, struct monst *mdef,
         if (!Blind)
             pline("%s is zapped!", Monnam(mdef));
         mhm->damage += destroy_mitem(mdef, WAND_CLASS, AD_ELEC);
-        if (resists_elec(mdef)) {
+        if (resists_elec(mdef) || defended(mdef, AD_ELEC)) {
             if (!Blind)
                 pline_The("zap doesn't shock %s!", mon_nam(mdef));
             golemeffects(mdef, AD_ELEC, mhm->damage);
@@ -2220,7 +2226,7 @@ mhitm_ad_elec(struct monst *magr, struct attack *mattk, struct monst *mdef,
         if (g.vis && canseemon(mdef))
             pline("%s gets zapped!", Monnam(mdef));
         mhm->damage += destroy_mitem(mdef, WAND_CLASS, AD_ELEC);
-        if (resists_elec(mdef)) {
+        if (resists_elec(mdef) || defended(mdef, AD_ELEC)) {
             if (g.vis && canseemon(mdef))
                 pline_The("zap doesn't shock %s!", mon_nam(mdef));
             shieldeff(mdef->mx, mdef->my);
@@ -2233,12 +2239,13 @@ mhitm_ad_elec(struct monst *magr, struct attack *mattk, struct monst *mdef,
 }
 
 void
-mhitm_ad_acid(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_acid(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     if (magr == &g.youmonst) {
         /* uhitm */
-        if (resists_acid(mdef))
+        if (resists_acid(mdef) || defended(mdef, AD_ACID))
             mhm->damage = 0;
     } else if (mdef == &g.youmonst) {
         /* mhitu */
@@ -2261,7 +2268,7 @@ mhitm_ad_acid(struct monst *magr, struct attack *mattk, struct monst *mdef,
             mhm->damage = 0;
             return;
         }
-        if (resists_acid(mdef)) {
+        if (resists_acid(mdef) || defended(mdef, AD_ACID)) {
             if (g.vis && canseemon(mdef))
                 pline("%s is covered in %s, but it seems harmless.",
                       Monnam(mdef), hliquid("acid"));
@@ -2279,8 +2286,9 @@ mhitm_ad_acid(struct monst *magr, struct attack *mattk, struct monst *mdef,
 
 /* steal gold */
 void
-mhitm_ad_sgld(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_sgld(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     struct permonst *pa = magr->data;
     struct permonst *pd = mdef->data;
@@ -3085,9 +3093,13 @@ mhitm_ad_ench(struct monst *magr, struct attack *mattk, struct monst *mdef,
 }
 
 void
-mhitm_ad_slow(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm UNUSED)
+mhitm_ad_slow(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm UNUSED)
 {
+    if (defended(mdef, AD_SLOW))
+        return;
+
     if (magr == &g.youmonst) {
         /* uhitm */
         int armpro = magic_negation(mdef);
@@ -3107,7 +3119,7 @@ mhitm_ad_slow(struct monst *magr, struct attack *mattk, struct monst *mdef,
         boolean uncancelled = !magr->mcan && (rn2(10) >= 3 * armpro);
 
         hitmsg(magr, mattk);
-        if (uncancelled && HFast && !defends(AD_SLOW, uwep) && !rn2(4))
+        if (uncancelled && HFast && !rn2(4))
             u_slow_down();
     } else {
         /* mhitm */
@@ -3930,10 +3942,10 @@ mhitm_ad_samu(struct monst *magr, struct attack *mattk, struct monst *mdef,
 
 /* disease */
 void
-mhitm_ad_dise(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_dise(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
-    struct obj *mwep;
     struct permonst *pa = magr->data, *pd = mdef->data;
 
     if (magr == &g.youmonst) {
@@ -3948,11 +3960,11 @@ mhitm_ad_dise(struct monst *magr, struct attack *mattk, struct monst *mdef,
             mhm->damage = 0;
     } else {
  mhitm_dise:
-        /* mhitm; protected monsters use the same criteria as for
-           poly'd hero gaining sick resistance combined with any hero
-           [hypothetically] wielding a weapon that guards against disease */
+        /* mhitm; protected monsters use the same criteria as for poly'd
+           hero gaining sick resistance combined with any hero wielding a
+           weapon or wearing dragon scales/mail that guards against disease */
         if (pd->mlet == S_FUNGUS || pd == &mons[PM_GHOUL]
-            || ((mwep = MON_WEP(mdef)) != 0 && defends(AD_DISE, mwep)))
+            || defended(mdef, AD_DISE))
             mhm->damage = 0;
         /* else does ordinary damage */
     }
@@ -3960,8 +3972,9 @@ mhitm_ad_dise(struct monst *magr, struct attack *mattk, struct monst *mdef,
 
 /* seduce and also steal item */
 void
-mhitm_ad_sedu(struct monst *magr, struct attack *mattk, struct monst *mdef,
-              struct mhitm_data *mhm)
+mhitm_ad_sedu(
+    struct monst *magr, struct attack *mattk,
+    struct monst *mdef, struct mhitm_data *mhm)
 {
     struct permonst *pa = magr->data;
 
diff --git a/src/worn.c b/src/worn.c
index a774b0b02..9252e33a8 100644
--- a/src/worn.c
+++ b/src/worn.c
@@ -337,7 +337,8 @@ mon_adjust_speed(struct monst *mon,
    but objects[ALCHEMY_SMOCK].oc_oprop can only describe one of them;
    if it is poison resistance, alternate property is acid resistance;
    if someone changes it to acid resistance, alt becomes posion resist;
-   if someone changes it to hallucination resistance, all bets are off */
+   if someone changes it to hallucination resistance, all bets are off
+   [TODO: handle alternate propertices conferred by dragon scales/mail] */
 #define altprop(o) \
     (((o)->otyp == ALCHEMY_SMOCK)                               \
      ? (POISON_RES + ACID_RES - objects[(o)->otyp].oc_oprop)    \
@@ -346,8 +347,11 @@ mon_adjust_speed(struct monst *mon,
 /* armor put on or taken off; might be magical variety
    [TODO: rename to 'update_mon_extrinsics()' and change all callers...] */
 void
-update_mon_intrinsics(struct monst *mon, struct obj *obj, boolean on,
-                      boolean silently)
+update_mon_intrinsics(
+    struct monst *mon,
+    struct obj *obj,   /* armor being worn or taken off */
+    boolean on,
+    boolean silently)
 {
     int unseen;
     uchar mask;
@@ -356,7 +360,7 @@ update_mon_intrinsics(struct monst *mon, struct obj *obj, boolean on,
         altwhich = altprop(obj);
 
     unseen = !canseemon(mon);
-    if (!which)
+    if (!which && !altwhich)
         goto maybe_blocks;
 
  again:
@@ -376,6 +380,7 @@ update_mon_intrinsics(struct monst *mon, struct obj *obj, boolean on,
         /* properties handled elsewhere */
         case ANTIMAGIC:
         case REFLECTING:
+        case PROTECTION:
             break;
         /* properties which have no effect for monsters */
         case CLAIRVOYANT:
@@ -384,16 +389,17 @@ update_mon_intrinsics(struct monst *mon, struct obj *obj, boolean on,
             break;
         /* properties which should have an effect but aren't implemented */
         case LEVITATION:
+        case FLYING:
         case WWALKING:
             break;
         /* properties which maybe should have an effect but don't */
         case DISPLACED:
         case FUMBLING:
         case JUMPING:
-        case PROTECTION:
             break;
         default:
-            if (which <= 8) { /* 1 thru 8 correspond to MR_xxx mask values */
+            /* 1 through 8 correspond to MR_xxx mask values */
+            if (which >= 1 && which <= 8) {
                 /* FIRE,COLD,SLEEP,DISINT,SHOCK,POISON,ACID,STONE */
                 mask = (uchar) (1 << (which - 1));
                 mon->mextrinsics |= (unsigned short) mask;
diff --git a/src/zap.c b/src/zap.c
index 56fc9eaac..5afd48f59 100644
--- a/src/zap.c
+++ b/src/zap.c
@@ -3757,7 +3757,7 @@ zhitm(
     *ootmp = (struct obj *) 0;
     switch (abstype) {
     case ZT_MAGIC_MISSILE:
-        if (resists_magm(mon)) {
+        if (resists_magm(mon) || defended(mon, AD_MAGM)) {
             sho_shieldeff = TRUE;
             break;
         }
@@ -3766,7 +3766,7 @@ zhitm(
             tmp = spell_damage_bonus(tmp);
         break;
     case ZT_FIRE:
-        if (resists_fire(mon)) {
+        if (resists_fire(mon) || defended(mon, AD_FIRE)) {
             sho_shieldeff = TRUE;
             break;
         }
@@ -3788,7 +3788,7 @@ zhitm(
         }
         break;
     case ZT_COLD:
-        if (resists_cold(mon)) {
+        if (resists_cold(mon) || defended(mon, AD_COLD)) {
             sho_shieldeff = TRUE;
             break;
         }
@@ -3801,6 +3801,7 @@ zhitm(
             (void) destroy_mitem(mon, POTION_CLASS, AD_COLD);
         break;
     case ZT_SLEEP:
+        /* possibly resistance and shield effect handled by sleep_monst() */
         tmp = 0;
         (void) sleep_monst(mon, d(nd, 25),
                            type == ZT_WAND(ZT_SLEEP) ? WAND_CLASS : '\0');
@@ -3825,18 +3826,18 @@ zhitm(
         } else {
             struct obj *otmp2;
 
-            if (resists_disint(mon)) {
+            if (resists_disint(mon) || defended(mon, AD_DISN)) {
                 sho_shieldeff = TRUE;
             } else if (mon->misc_worn_check & W_ARMS) {
                 /* destroy shield; victim survives */
                 *ootmp = which_armor(mon, W_ARMS);
             } else if (mon->misc_worn_check & W_ARM) {
-                /* destroy body armor, also cloak if present */
+                /* destroy suit, also cloak if present */
                 *ootmp = which_armor(mon, W_ARM);
                 if ((otmp2 = which_armor(mon, W_ARMC)) != 0)
                     m_useup(mon, otmp2);
             } else {
-                /* no body armor, victim dies; destroy cloak
+                /* no suit, victim dies; destroy cloak
                    and shirt now in case target gets life-saved */
                 tmp = MAGIC_COOKIE;
                 if ((otmp2 = which_armor(mon, W_ARMC)) != 0)
@@ -3850,7 +3851,7 @@ zhitm(
         tmp = mon->mhp + 1;
         break;
     case ZT_LIGHTNING:
-        if (resists_elec(mon)) {
+        if (resists_elec(mon) || defended(mon, AD_ELEC)) {
             sho_shieldeff = TRUE;
             tmp = 0;
             /* can still blind the monster */
@@ -3874,14 +3875,14 @@ zhitm(
             (void) destroy_mitem(mon, RING_CLASS, AD_ELEC);
         break;
     case ZT_POISON_GAS:
-        if (resists_poison(mon)) {
+        if (resists_poison(mon) || defended(mon, AD_DRST)) {
             sho_shieldeff = TRUE;
             break;
         }
         tmp = d(nd, 6);
         break;
     case ZT_ACID:
-        if (resists_acid(mon)) {
+        if (resists_acid(mon) || defended(mon, AD_ACID)) {
             sho_shieldeff = TRUE;
             break;
         }