# Blue jelly

j blue jelly 

Difficulty

5

Attacks

Passive (level + 1)d6 cold

j blue jelly 

Difficulty

5

Attacks

Passive (level + 1)d6 cold

Base level

4

Base experience

45

Speed

0

Base AC

8

Base MR

10

Alignment

0 (neutral)

Frequency (by normal means)

2 (Quite rare)

Genocidable

Yes

Weight

50

Nutritional value

20

Size

Medium

Resistances

Cold, poison

Resistances conveyed

Cold (13%), poison (13%)

A blue jelly:

 can flow under doors.

 does not breathe.
 cannot pick up items.
 has no eyes.

 has no limbs.
 has no head.
 is mindless.

 does not eat. (*)
 is neither male nor female.
 is normally generated hostile.

Reference

monst.c#line503

A blue jelly, j, is a type of monster that appears in NetHack. Like most jellies, it is eyeless, amorphous, and sessile, and cannot actively attack, but it possesses a cold passive attack that triggers if you or a monster attack one in melee.
If you or a monster attack a blue jelly and lack cold resistance, and the attack does not kill the jelly, its passive attack deals cold damage depending on its base level and increases the jelly's HP by half the damage inflicted.[1][2] If enough HP is gained from this the jelly will undergo division, halving its HP and creating a second jelly with the same amount of HP.[3]
Blue jelly corpses and tins are vegan, and eating one may convey cold resistance or poison resistance.

Contents

1 Generation
2 Strategy
3 History
4 Encyclopedia entry
5 References

Generation
In addition to random generation and division, blue jellies may appear among the various jellies generated as the second quest monster class for the Knight quest, which makes up 3% of randomly generated monsters.

Strategy
Avoid attacking a blue jelly in melee unless you have cold resistance, as blue jellies are much tougher than might be expected, and their cold passive attack can be deadly to inexperienced players. At their base level, they do (4+1)d6 damage, which gives a range of 5–30, and they can be generated at much higher levels.
While ranged attacks are preferable, but make sure you have enough options to finish the job—you won't be able to retrieve that lovely stack of daggers until the jelly is dead. The aklys is a solid option that likely should be used first - at worst, the aklys has a 1% chance that it will fail to return, but you will most likely do enough damage that you can kill the jelly with any remaining projectiles, preserving valuable darts, wand charges and/or other items.
Blue jellies are frequently employed for boulder forts, stashes, and the like since they are completely immobile.

History
The blue jelly first appears in NetHack 3.0.0.

Encyclopedia entry

I'd planned how to prevent the lock from sealing behind me; it required a temporary sacrifice, not cleverness.  I used the door itself to help me cut off a portion of my body, after shunting all memory from the piece to be abandoned.  The piece, looking inexpressibly dear and forlorn for a bit of blue jelly, would force open the outer door until I returned and rejoined it.

[ Beholder's Eye, by Julie E. Czerneda ] 

References

↑ src/uhitm.c in NetHack 3.6.7, line 2447: case for cold passive against you

↑ src/mhitm.c in NetHack 3.6.7, line 1671: case for cold passive against monsters

↑ src/potion.c in NetHack 3.6.7, line 2379