# Deep one
Deep ones are new monsters added in SLASH'EM and dNetHack. There is a large level difference between the deep ones and deepest ones, so once you are experienced enough for deep ones to appear you will likely encounter them in some form until the end game. This also means that if a lower level character manages to tame a deep one (which is not difficult as their MR is only 10), they will eventually have a level 45 pet deepest one. All deep ones are capable of treachery, but will eat corpses and thus are relatively easy to keep tame.
The deep one is the only form that is capable of wearing body armor and cloaks, and all forms can wear all other types of armor. If a deep one wearing body armor grows up into a deeper one, the body armor is not destroyed as with polymorphing into a larger size, so it is possible to raise a deepest one that wears a full ascension kit of armor.
Deep ones are capable of swimming and will also be frequently generated on the Plane of Water.
Deep(er, est) ones play a much greater role in dNethack. They are abundantly generated on the Anachrononaut quest, complete with firearms and other future weapons.  They are also generated in the the Gulf of N'Kai in the Neutral Quest.  In addition, deep and deeper ones can be spawned in a dNethack throne room, with a deepest one as the overlord.
In addition, they each have a passive on-death effect. When a deep one dies, every other deep(er, est) one on the level receives +2 max hp. Deeper ones give +4, and deepest ones give +8. If this is enough to bring them to a new level threshold, they'll grow up into the next stage of evolution and deal more damage. This only applies to monsters currently on the level though, so it won't apply to monsters generated in the future.

Contents

1 Deep one
2 Deeper one
3 Deepest one
4 Mythology
5 Encyclopedia Entry

Deep one

h deep one 

Difficulty

9

Attacks

Claw 1d6, Claw 1d6, Bite 2d4

h deep one 

Difficulty

9

Attacks

Claw 1d6, Claw 1d6, Bite 2d4

Base level

7

Base experience

92

Speed

9

Base AC

5

Base MR

10

Alignment

−5 (chaotic)

Frequency (by normal means)

2 (Quite rare)

Genocidable

Yes

Weight

1500

Nutritional value

400

Size

Medium

Resistances

cold, poison

Resistances conveyed

poison (47%)

A deep one:

 can swim.

 can survive underwater.

 has a head, a couple of arms, and a torso.

 is poisonous to eat.

 is omnivorous.

 is normally generated hostile.

 can follow you to other levels.

 likes gold.
 likes gems.
 can pick up weapons and food.
 can pick up magical items.

 has infravision.
 can be seen through infravision.

 normally appears in large groups.

 may turn against you when tame.

Reference

SLASH'EM_0.0.7E7F2/monst.c#line807

In dNetHack, they are slightly changed, with a 1d6 weapon attack, a 1d6 offhand weapon attack, and a 2d4 kick.

Deeper one

h deeper one 

Difficulty

18

Attacks

Claw 3d4, Claw 3d4, Bite 4d6

h deeper one 

Difficulty

18

Attacks

Claw 3d4, Claw 3d4, Bite 4d6

Base level

15

Base experience

388

Speed

12

Base AC

0

Base MR

30

Alignment

−7 (chaotic)

Frequency (by normal means)

2 (Quite rare)

Genocidable

Yes

Weight

2000

Nutritional value

500

Size

Large

Resistances

cold, poison

Resistances conveyed

poison (100%)

A deeper one:

 can swim.

 can survive underwater.

 has a head, a couple of arms, and a torso.

 is poisonous to eat.

 is omnivorous.

 is a lord to its kind.

 is normally generated hostile.

 can follow you to other levels.

 is strong.

 likes gold.
 likes gems.
 can pick up weapons and food.
 can pick up magical items.

 has infravision.
 can be seen through infravision.

 normally appears in small groups.

 may turn against you when tame.

Reference

SLASH'EM_0.0.7E7F2/monst.c#line834

In dNetHack, they are slightly changed, with a 3d4 weapon attack, a 3d4 offhand weapon attack, and a 4d6 kick.

Deepest one

h deepest one 

Difficulty

33

Attacks

Claw 3d6, Claw 3d6, Bite 5d6

h deepest one 

Difficulty

33

Attacks

Claw 3d6, Claw 3d6, Bite 5d6

Base level

30

Base experience

1188

Speed

15

Base AC

−5

Base MR

70

Alignment

−9 (chaotic)

Frequency (by normal means)

1 (Very rare)

Genocidable

Yes

Weight

3000

Nutritional value

500

Size

Huge

Resistances

cold, poison

Resistances conveyed

poison (100%)

A deepest one:

 can swim.

 can survive underwater.

 has a head, a couple of arms, and a torso.

 has a thick hide.

 is poisonous to eat.

 is omnivorous.

 is an overlord to its kind.

 is normally generated hostile.

 can follow you to other levels.

 is strong.

 likes gold.
 likes gems.
 can pick up weapons and food.
 can pick up magical items.

 has infravision.
 can be seen through infravision.

 may turn against you when tame.

Reference

SLASH'EM_0.0.7E7F2/monst.c#line843

In dNetHack, they are mildly buffed, with a 3d8 weapon attack and 3d8 offhand weapon attack instead of 3d6 claws. The 5d6 kick is the same.

Mythology
The deep one and its related kin all come from "The Shadow over Innsmouth" by H.P. Lovecraft, creator of the Cthulhu mythos.
They are intelligent ocean-dwelling creatures, and are fishy/froggy humanoids in appearance. The transition from deep one to deepest one in-game is a reference to the deep one-like giants in Lovecraft's earlier short story "Dagon."  Deep ones are immortal, and in the wider Cthulhu mythos it is accepted that they grow continuously throughout their lives.  The oldest deep ones, therefore, would be very large indeed, thus explaining both the human-sized deep ones in "Innsmouth" and the whale-sized giants living in the deep ocean in "Dagon."

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Encyclopedia Entry

For eighty thousand years Pth'thya-l'yi had lived in Y'ha-nthlei, and thither she had gone back after Obed Marsh was dead. Y'ha-nthlei was not destroyed when the upper-earth men shot death into the sea.  It was hurt, but not destroyed.  The Deep Ones could never be destroyed, even though the palaeogean magic of the forgotten Old Ones might sometimes check them.  For the present they would rest; but some day, if they remembered, they would rise again for the tribute Great Cthulhu craved.

[ The Shadow Over Innsmouth, by H.P. Lovecraft ] 