Sack of spiders

Version 0.21: This article may not be up to date for the latest stable release of Crawl.

Type	Miscellaneous item
Name	sack of spiders
Icon

A woven silk bag. Opening it will release a number of spiders and other insects, as well as creating webs nearby. Evocations skill increases its effectiveness. There is a one in three chance of accidentally destroying the sack when using it.

A sack of spiders is an evokable item which, when used, generates a Spider's Nest-themed group of friendly monsters, and also generates multiple web traps on hostile monsters in your line of sight. Evocations skill affects both the strength and number of summoned allies.

The success rate depends on Evocations: it is 30% at 0 skill, 60% at 10, 70% at 18, and 77% at 27.

The chance to destroy the sack on each use is 1/3 (regardless of Evocations skill).

Potential Results

Each successful use of a sack of spiders is guaranteed to produce at least 1-2 allies, plus an additional 1d(Evocations / 3) - 1.

A table of potential results versus example amounts of Evocations skill:

Monster	Min. Skill	Max. Skill		Skill 0	Skill 3	Skill 6	Skill 9	Skill 12	Skill 15	Skill 18	Skill 21	Skill 24	Skill 27
B Worker ant	0	13		16.67%	15.18%	7.66%	1.79%	0%	0%	0%	0%	0%	0%
B Soldier ant	0	13		83.33%	84.82%	52.68%	21.54%	7.53%	1.48%	0%	0%	0%	0%
s Redback	6	19		0%	0%	39.66%	57.92%	56.7%	33.41%	12.25%	0%	0%	0%
s Redback	8	27		0%	0%	0%	18.75%	28.69%	36.07%	33.04%	18.21%	12.53%	11.76%
s Jumping spider	10	27		0%	0%	0%	0%	7.09%	22.28%	28.57%	22.49%	15.48%	14.53%
s Orb spider	12	29		0%	0%	0%	0%	0%	6.76%	19.83%	27.31%	18.8%	17.64%
s Tarantella	13	29		0%	0%	0%	0%	0%	0%	6.31%	19.86%	23.93%	22.45%
s Wolf spider	15	29		0%	0%	0%	0%	0%	0%	0%	12.14%	29.25%	27.44%
y Ghost moth	21	27		0%	0%	0%	0%	0%	0%	0%	0%	0%	6.17%

Strategy

• A sack of spiders is nearly useless without at least 8 or so levels of Evocations. If you haven't put in the training, don't expect any results from this beyond a couple of quickly destroyed meat shields.
• Be careful where you move after using a sack of spiders. Stepping into one of your own generated web traps is a good way to earn yourself YASD.

History

• Prior to 0.19, sacks of spiders didn't stack. Instead, each sack of spiders had 5-15 charges.
• Prior to 0.18, there were giant mites, spiders and trapdoor spiders summoned if you evocation was still low.
• In 0.15, the webs created when evoking a sack of spiders will target enemies, rather than being placed randomly.
• Sacks of spiders were added in 0.13.