Explicitly list the random breath types

include/extern.h

@@ -1657,6 +1657,7 @@ extern boolean resist_conflict(struct monst *);
 extern boolean mon_knows_traps(struct monst *, int);
 extern void mon_learns_traps(struct monst *, int);
 extern void mons_see_trap(struct trap *);
+extern int get_atkdam_type(int);
 
 /* ### monmove.c ### */
 

src/mondata.c

@@ -1416,4 +1416,16 @@ mons_see_trap(struct trap *ttmp)
     }
 }
 
+int
+get_atkdam_type(int adtyp)
+{
+    if (adtyp == AD_RBRE) {
+        static const int rnd_breath_typ[] = {
+            AD_MAGM, AD_FIRE, AD_COLD, AD_SLEE,
+            AD_DISN, AD_ELEC, AD_DRST, AD_ACID };
+        return rnd_breath_typ[rn2(SIZE(rnd_breath_typ))];
+    }
+    return adtyp;
+}
+
 /*mondata.c*/

src/mthrowu.c

@@ -893,8 +893,7 @@ breathwep_name(int typ)
 int
 breamm(struct monst* mtmp, struct attack* mattk, struct monst* mtarg)
 {
-    /* if new breath types are added, change AD_ACID to max type */
+    int typ = get_atkdam_type(mattk->adtyp);
-    int typ = (mattk->adtyp == AD_RBRE) ? rnd(AD_ACID) : mattk->adtyp ;
 
     if (m_lined_up(mtarg, mtmp)) {
         if (mtmp->mcan) {