# Growing up
Growing up is the process in which a monster turns into a larger version of itself (e.g., a kitten turns into a housecat). Monsters grow from killing monsters and gaining levels, from the effects of a potion of gain level, or from wraith corpses.

Contents

1 Natural growth

1.1 Examples

2 Magical growth
3 Changing form
4 Variants

4.1 SLASH'EM
4.2 UnNetHack
4.3 SpliceHack

5 References

Natural growth
If a monster kills another monster, its maximum and current HP will both increase.[1]  If its maximum hp are increased above the threshold for its current level, it will gain a level.  There is a limit to maxhp and levels a monster can gain in this way.
The monster will increase maxhp by d(victim level + 1), but no more than enough to bring it to the minimum for the next level.  Current hp will increase by d(increase in maxhp) - 1.
The hp threshold for most monsters is 8 * current level (4 for level 0).  Exceptions are golems and elementals on their home plane.
The maximum level attainable via this method is 3/2 of the base level for the current monster type (or the next type if there is a more "grown up" form), but no less than 5 and normally no greater than 49.[2]  Player monsters can reach level 30, and monsters which have a minimum level greater than 49 (named demons) have a maximum level of 50.  If an increase in maxhp would increase the monster's level above this maximum, its maxhp are reset to the threshold for its current level.

Examples
a dog (currently level 4, maxhp 31) kills a kobold shaman (level 2). Its maxhp can increase by 1-3. If it gains 2-3 maxhp, it will become level 5, with maxhp of 33.
a large dog (currently level 9, maxhp 70) kills a dwarf king (level 6) and would gain 4 maxhp.  Its maxhp do not increase beyond 72.

A user has suggested improving this page or section as follows:
"It would be nice to have a table on a separate page of each monster and its "natural" maximum level and hp"

Magical growth
A monster drinking a potion of gain level or eating a wraith corpse will gain a level and increase its current and maximum hp by d8. 
Monsters may exceed their natural level limit in this way, although they may not exceed a hard limit of 49 (50 for named demons). Additionally, pets eating wraith corpses cannot exceed their base level by 15[3] (but engulfing live wraiths still works[4]). They may subsequently increase their maximum HP to the cap for their new level by killing monsters.

Changing form
If a monster gains a level so that its current level equals or exceeds the minimum level of its next available form, it will "grow up" into that form (e.g. a little dog which reaches level 4 will become a dog.) If you can see or detect the monster, you will receive a message to that effect: "The kitten grows up into a housecat" or "The soldier becomes a sergeant".

Growing up does not allow a monster to take a genocided form. If the new form is genocided, the monster dies and does not leave a corpse. Extinct forms are nonetheless allowed.[5] This will generate the message "As foo grows up into foo, s/he 

<expires dies="">!" if you can see or otherwise detect the monster.
Growing up is a one-way process, and level draining a grown-up monster will not cause it to revert to a lesser form. The only possible way for a monster to retake its previous form is polymorphing them, which yields no real benefit.
While many players may only ever notice the growth of domestic pets (dogs, cats, and horses), a surprising number of monsters can grow up in this manner. The possible form changes are as follows:[6]
Domestic animals:

little dog → dog → large dog
kitten → housecat → large cat
pony → horse → warhorse
Baby monsters:

chickatrice → cockatrice
hell hound pup → hell hound
winter wolf cub → winter wolf
baby gray dragon → gray dragon
baby silver dragon → silver dragon
baby shimmering dragon → shimmering dragon (deferred)
baby red dragon → red dragon
baby white dragon → white dragon
baby orange dragon → orange dragon
baby black dragon → black dragon
baby blue dragon → blue dragon
baby green dragon → green dragon
baby yellow dragon → yellow dragon
baby gold dragon → gold dragon (NetHack 3.7.0)
red naga hatchling → red naga
black naga hatchling → black naga
golden naga hatchling → golden naga
guardian naga hatchling → guardian naga
baby long worm → long worm
baby purple worm → purple worm
baby crocodile → crocodile
Orcs and elves:

orc / hill orc / Mordor orc / Uruk-hai → orc-captain
elf / Woodland-elf / Green-elf / Grey-elf → elf-lord → elvenking
Other humanoids:

kobold → large kobold → kobold lord
gnome → gnome lord → gnome king
dwarf → dwarf lord → dwarf king
ogre → ogre lord → ogre king
mind flayer → master mind flayer
Undead:

lich → demilich → master lich → arch-lich
vampire → vampire lord
manes → lemure
Giant animals:

sewer rat → giant rat
cave spider → giant spider
bat → giant bat
Soldiers, Kops and watchmen:

soldier → sergeant → lieutenant → captain
Keystone Kop → Kop Sergeant → Kop Lieutenant → Kop Kaptain
watchman → watch captain
Quest guardians:

student → archeologist
attendant → healer
page → knight
acolyte → priest
apprentice → wizard
Other:

small mimic → large mimic → giant mimic
aligned priest → high priest
Although queen bees can lay killer bee eggs, and winged gargoyles can lay gargoyle eggs, such offspring are sterile and will not grow into their parent forms.

Variants
SLASH'EM
Several monsters added in SLASH'EM also are capable of growing up

pile of killer coins → large pile of killer coins → huge pile of killer coins
dingo puppy → dingo → large dingo
larva → maggot → dung worm
giant tick → giant flea → giant louse
deep one → deeper one → deepest one
lamb → sheep
shoggoth → giant shoggoth
gnoll → gnoll warrior → gnoll chieftain
migo drone → migo warrior
vampire lord → vampire mage
baby shimmering dragon → shimmering dragon
baby deep dragon → deep dragon
gnome lord → gnome warrior (This is a change from vanilla)
UnNetHack
sewer rat → giant rat → rodent of unusual size
In the Convict patch and some other variants that include it, the giant rat grows up into the enormous rat before it becomes the rodent of unusual size. In the latest version of the UnNetHack source code, however, the enormous rat has been removed and giant rats now grow up directly into R.O.U.S.

SpliceHack
SpliceHack adds new monsters that can grow up, and gives some monsters from vanilla the ability to grow up:[7]

little dog → dog → large dog → guard dog
winter wolf pup → winter wolf cub → winter wolf
kitten → housecat → large cat → fat cat
sewer rat → giant rat → rodent of unusual size
zoo bat → gaol bat
baby violet dragon → violet dragon
crocodile → killer croc
ichneumon larva → giant ichneumon
grid bug → spark bug → arc bug → lightning bug
manes → lemure
rock piercer → iron piercer → glass piercer → diamond piercer
dust vortex → dust devil
werewolf → pack lord
deep one → deeper one → deepest one
pig → feral hog
ratman → ratman squeaker
giant spider → monstrous spider
maggot → giant fly
kraken → thing from below
ghost → spectre
martial artist → grandmaster
movanic deva → monadic deva → astral deva
shrieker → screamer
red mold → red moldier
yellow mold → yellow moldier
green mold → green moldier
brown mold → brown moldier
ghoul → ghast
References

↑ grow_up in makemon.c

↑ src/makemon.c in NetHack 3.6.0, line 1700

↑ src/dogmove.c in NetHack 3.6.0, line 336

↑ meatobj in mon.c

↑ src/makemon.c in NetHack 3.6.0, line 1731

↑ grownups data structure in mondata.c

↑ https://github.com/NullCGT/SpliceHack/blob/Spl-R-1.1.0/src/mondata.c#L1070

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