In vanilla, stoning resistance can only be gained by polymorphing into an intrinsically stoning resistant monster, not by any other means (such as equipment or eating corpses). You are only resistant for the duration you are such a monster. Intrinsic stoning resistance is not implemented.
A variety of monsters are stoning-resistant, typically for fairly straightforward reasons:
- Creatures that can petrify others: chickatrices, cockatrices, and Medusa (but Medusa can be stoned by her own reflection)
- Creatures already made of stone or earth: gargoyles, winged gargoyles, stone golems, earth elementals, xorns
- Creatures that are acidic: acid blobs, black naga hatchlings, black nagas, gelatinous cubes, green molds, Juiblex, ochre jellies, spotted jellies, baby yellow dragons, yellow dragons, all P
- Immaterial creatures: air elementals, djinn, sandestins, mail daemons, fire elementals, ghosts, shades, water elementals, wraiths, lights, all v
- Important enemies: Death, Famine, Pestilence, and all quest nemeses
- Lizards (logically enough, since they cure stoning when eaten)
- Skeletons (presumably fossilization doesn't slow them down much)
If you try to petrify any other golems, they instead become stone golems.
Stiffening versus instadeath
Touching a cockatrice or chickatrice is instantly fatal for a character without stoning resistance, as is meeting the gaze of Medusa. Attacking a cockatrice or chickatrice barehanded or barefooted, picking up the corpse barehanded, and kicking it barefooted are ways of touching among many, many others. Throwing a cockatrice egg up (<) and being hit by it is an instadeath, but being hit by one thrown by a monster starts the stiffening process, as does eating the egg, or hearing the cockatrice's hissing attack. The process technically takes 5 turns, but after 2, your limbs turn to stone and you can't do anything else but proceed to die. You will also lose any intrinsic speed when you start "slowing down", which may give you even fewer actions to save yourself; if you are burdened or worse, you might not be able to save yourself at all!
|Message||Turns to live|
|"You are slowing down"||2|
|"Your limbs are stiffening"||1|
If you hear the hissing of a cockatrice and start turning to stone – stiffening – you still have several ways, albeit not several turns, to save yourself. The corpse of a lizard or an acidic monster stops the process as soon as you start eating, so you shouldn't worry about not chewing fast enough or being interrupted. The monster corpses that can stop stiffening are as follows:
- (baby) yellow dragon
- black naga (hatchling)
- acid blob
- gelatinous cube
- spotted jelly
- ochre jelly
- green mold
- gray ooze
- brown pudding
- black pudding
- green slime – but see below.
Tins of the above monsters will also work. However, they need to be blessed in order to have a chance of saving your life; blessed tins take one turn to open and a second turn to eat, while non-blessed tins take more than one turn to open (unless you are wielding a tin opener – but you do not have enough time to wield one if you weren't already).
The most common method is to eat a lizard corpse; since they never rot, you should always carry one along.
However, if you do not have an appropriate corpse with you, you may also quaff a potion of acid. The stone to flesh spell will save you if you cast it on yourself, but it will also turn mineral items in your main inventory to meat, including rocks, rings, and wands.
An amulet of unchanging will not protect you from stoning, but an amulet of life saving will save your life. Reflection or blindness protects you from turning to stone by the gaze of Medusa. Wearing gloves is strongly recommended while handling cockatrices.
Polymorphing into a stoning-resistant monster will also stop the petrification process, as will polymorphing into any type of golem (as they turn into stone golems rather than dying).
In SLASH'EM, there are two additional monsters that cause stoning: the thick-hided basilisk, and the asphynx, which can hide under objects and stone an unsuspecting player. Both are significantly higher-level than the cockatrice; on average, fights against them will be longer, increasing the chance that one of their attacks may start turning you to stone. They also use different glyphs, meaning that a blessed scroll of genocide is no longer an easy solution.
SLASH'EM also introduces the amulet versus stone, which will save your life against stoning in the same manner as an amulet of life saving, costing a point of constitution and incrementing the "killed" counter. The amulet, however, is not destroyed in the process unless it is cursed; otherwise, its beatitude changes from uncursed to cursed, or from blessed to uncursed. Thus, with a sufficient supply of holy water, one amulet can prevent many stoning YASDs.
dNetHack introduces several new acidic monsters, whose corpses can cure stoning:
- blood bloaters
- blue and yellow dragons and baby forms (blue is new)
- flux slime
- darkness given hunger
Monks gain intrinsic stoning resistance at level 27.
- monst.c, line 147, monst.c, line 184, monst.c, line 176, monst.c, line 426, monst.c, line 433, monst.c, line 1349, monst.c, line 1423, monst.c, line 1744, monst.c, line 1774, monst.c, line 2063, monst.c, line 2477, monst.c, line 2879, monst.c, line 3220
- See monst.c, line 94 and on; look for MR_STONE in the seventh field (not the eighth, that's resistances it grants).
- timeout.c in NetHack 3.4.3, line 36
- src/eat.c in NetHack 3.6.1, line 704, src/eat.c in NetHack 3.6.1, line 733