Parasitology

In dNetHack, notdNetHack and notnotdNetHack, parasitology is a research path available to characters that have the weed thought slotted and with at least 27 insight, necessary to activate the thought. Neutral Undead Hunters start each game with the thought already slotted. It is also referred to as the philosophy of the choir.

Description

To progress along the research path, a character must research corpses of non-mindless, non-animal monsters at workbenches, or with a dissection kit. Corpses that have been researched, or that haven't been researched and decayed, may yield a number of parasites, which are required to obtain parasitology upgrades. For non-Undead Hunters, following the parasitology research path requires wishing for the thought and dissection kit.

Upgrades are not linear, and may be chosen any number of times, except "visions of Yog-Sothoth". Once enough research has been performed, a character may obtain a parasitology upgrade by applying a trephination kit with a parasite held in open inventory:

• Suck out your enemies' brains: Adds a 1d2 intelligence-draining attacks to your melee attack routine per parasite.
• Empower charm spells: Increases your skill with enchantment spells. Increases the odds of taming a monster for the charm monster spell for every third time this upgrade is taken. Decreases spell failure for enchantment spells by another 5%.
• Empower explosive spells: Increases the amount of rays produced by ray spells.
• Multi-shoot ray and beam spells: Increases the amount of explosions produced by explosion spells.
• Sting adjacent enemies: Adds a 1d1 passive pain-inflicting tentacle attack per parasite. Makes 1 attack roll against every adjacent monster, and another for every third parasite rounding up. Each attack has a flat ¹⁄₂ chance of skipping out on the attack. The stingers also only make at most 2 attacks per monster for every implanted parasite.
• Embrace the visions of Yog-Sothoth: Allows Undead Hunters to ask for the "windows to other places" Yog-Sothoth boon without meeting lifetime devotion thresholds, and any number of times. The upgrade can only be selected once

All parasitology upgrades, except "visions of Yog-Sothoth", decrease spell failure rate of all spells by 5%.

Undead Hunters that wish to ascend under the Choir, must have claimed at least 6 upgrades to achieve a full-scoring ascension. Other roles can obtain parasitology upgrades, but cannot ascend under an Undead Hunter ascension.

Obtaining any upgrade also reduces current and peak intelligence and wisdom scores by 1. Every third upgrade taken on the research path will also permanently reduce the maximum intelligence and wisdom possible for that character by 1; this also stacks with reductions from defilement research. Fully advancing along the parasitology research path will reduce their intelligence and wisdom maximums by 4, producing a cap of 21 for each compared to the normal 25.

The spells considered "advanced explosion" for the purposes of the table below are firestorm, blizzard and lightning storm.

Rays and explosions gained per parasite:
Parasites:	Advanced explosion spells	Explosion spells	Ray spells
1	+1	+1 (50%)	+1 (50%)
2	+2	+1	+1
3	+3	+1 + 1 (33%)	+1 + 1(33%)
4	+4	+1 + 1 (66%)	+1 + 1 (66%)
5	+5	+2	+2
6	+6	+2 +1 (33%)	+2 +1 (33%)
7	+7	+2 +1 (66%)	+2 +1 (66%)
8	+8	+3	+3
9	+9	+3	+3
10	+10	+3 +1 (25%)	+3 +1 (25%)

Messages

You leave a seam so the parasite's radula can reach out.

You implanted a brainsucker.

You put the parasite in your medial prefrontal cortex.

You improved your enchantment spellcasting skill.

You put the parasite in your speech center.

You increased the amount of explosions produced by spells.

You put the parasite in your motor cortex.

You increased the amount of rays produced by spells.

You leave the parasite's stinging guard tentacles sticking out.

You implanted a jellyfish stinger.

You put the parasite in your corpus callosum.

You obtained the Yog-Sothoth upgrade.

Enlightenment messages:

You have positioned <number> parasites to suck out your enemies' brains.

You have positioned <number> parasites to empower your charm spells.

You have positioned <number> parasites to empower your explosive spells

You have positioned <number> parasites to empower your ray and beam spells

You have positioned <number> parasites to sting adjacent enemies