Potions are often destroyed when dropped onto very hot ground

In Gehennom and on the Plane of Fire, the ground is hot enough to
boil potions (although not hot enough to, e.g., burn scrolls).
The potions sometimes survive this (almost always if it's your
potion, it's blessed, and you have maxed Luck), but often don't.

In addition to making a lot of flavour sense, this serves a
gameplay purpose in that it reduces the number of potions that
are deathdropped by monsters in the late game. In Gehennom,
monsters often generate with potions to use defensively, but then
get killed before they have a chance to use them: this produces a
surfeit of potions that players tend to convert into holy water or
potions of full healing (and in general it doesn't make much sense
that the basic potion of healing primarily generates in Gehennom).
This commit approximately halves the number of useful potion
deathdrops, whilst still allowing monsters access to their
potions; when the monster dies, it drops the potion and this has a
chance of destroying it.

doc/fixes3-7-0.txt

@@ -2378,6 +2378,7 @@ allow the ')', '[', '(', '=', '"', and '*' commands to be preceded by the 'm'
 	prefix to force a menu where the player can pick an item and choose
 	a context-sensitive item action for it; some give a menu even without
 	the prefix and for those, same item selection and action can be used
+hot ground (Gehennom / Plane of Fire) often destroys dropped potions
 
 
 Platform- and/or Interface-Specific New Features

src/do.c

@@ -303,6 +303,34 @@ flooreffects(struct obj *obj, coordxy x, coordxy y, const char *verb)
     } else if (gc.context.mon_moving && IS_ALTAR(levl[x][y].typ)
                && cansee(x,y)) {
         doaltarobj(obj);
+    } else if (obj->oclass == POTION_CLASS && gl.level.flags.temperature > 0 &&
+               (levl[x][y].typ == ROOM || levl[x][y].typ == CORR)) {
+        /* Potions are sometimes destroyed when landing on very hot
+           ground. The basic odds are 50% for nonblessed potions and
+           30% for blessed potions; if you have handled the object
+           (i.e. it is or was yours), these odds are adjusted by Luck
+           (each Luck point affects them by 2%). Artifact potions
+           would not be affected, if any existed. */
+        if (cansee(x,y)) {
+            /* unconditional "ground" is safe as this only runs for
+               room and corridor tiles */
+            pline("%s up as %s the hot ground.", Tobjnam(obj, "heat"),
+                  is_plural(obj) ? "they hit" : "it hits");
+        }
+
+        int survival_chance = obj->blessed ? 70 : 50;
+        if (obj->invlet) survival_chance += Luck * 2;
+
+        if (!obj_resists(obj, survival_chance, 100)) {
+            if (cansee(x,y)) {
+                pline("%s from the heat!",
+                      is_plural(obj) ? "They shatter" : "It shatters");
+            } else {
+                You_hear("a shattering noise.");
+            }
+            breakobj(obj, x, y, FALSE, FALSE);
+            res = TRUE;
+        }
     }
 
     gb.bhitpos = save_bhitpos;