The Altar of Pthoatl-Gree

A dark vision of insanity over at the Black Gate.  Reminds me of William Gibson's Lovecraftian tale "Hinterlands".  Here's my own version of ready-to-use game material.

Appearance

Explorers in different ages, delving in vastly different subterranean locations, have made similar reports of a strange altar-like arrangement.  The main feature of the altar is an idol, in the form of a hideous crouching, grinning entity.  Before the idol, is a large, cylindrical compartment, which may be opened/closed via rotation.

Both the idol and box are carved from a single, enormous black stone block.  The block is covered in hieroglyphs depicting strange entities of countless forms placing offerings of money in the box.  The next panel is invariably the same creature extracting some item from the box.  The coins in the hieroglyphics contain flecks of pyrite and glitter with a bit of a gold-ish color.

The close observer may notice that the number of coins in each subsequent hieroglyph is steadily increasing: 1, 1, 2, 3, 5, 8..

Some of the explorers report the altar being gone on subsequent visits, despite no obvious means of egress for the colossal stone arrangement.  (Any time the party  returns to room, there is a 10% chance it will no longer be there)

Mechanics

If gold coins are placed within the compartment and the compartment closed, then after 1d100 minutes, there will be an effect.  If any other item is placed within(or gold coins and some other item) then there is no effect.

If there was not a Fibonacci number of gold coins, use this table:

1. Explosion upon opening(Save or Die for creature opening it)
2. Liquid begins pouring out upon opening(1d100x1d100x1000 liters(1000 L per minute) of: 1-fresh water, 2-acid, 3-lava, 4-fruit juice, 5-blood, 6-seawater(with strange creatures in it), 7-sticky ichor, 8-poisonous liquid)
3. Altar disappears from this location
4. Violent Earthquake(each room/passage in dungeon has 10% chance of collapsing.  Collapse occurs in 1d10 rounds)

If there was a Fibonacci number of gold coins(1,1,2,3,5...10946), then when the compartment is opened, the coins will be gone and in their place will be an item.  Each Fibonacci number will only work once(except 1 which will work twice.  In general, higher Fib(X) values will yield more potent results:

Form: 

1. food item
2. drink item
3. creature
4. device
5. adventuring equipment(weapon/armor/etc)
6. text(tablet, scroll, book)

Commonality(roll 1d100+5X):

• 1-33 ordinary(common on this planet)
• 34-67 rare(rare on this planet)
• 68-100 extraterrestrial(similar to something on this planet, but slightly different)
• 101-150 alien(something strange, no resemblance to anything of this planet)
• 151-200 other-dimensional(something from another dimension)

Effect(roll 1d100+5X):

• 1-50 inert
• 51-100 beneficial
• >100- detrimental

 

An Example

OK, let's make a table of effects of different Fibonacci numbers of coins:

.	X	Fib(X)=Number of GP	Form	Commonality	Effect	Item
.	1	1	creature	ordinary	beneficial	A rather large, black housecat. Petting it causes character to be 'blessed' for 1d10 rounds
.	2	1	device	extraterrestrial	beneficial	Field glasses, apparently for a 3-eyed creature. Provides electro-optic magnification x2-x200
.	3	2	food	ordinary	inert	red apple
.	4	3	device	rare	beneficial	Silk Rope(400ft) Moves as snake to obey simple orders
.	5	5	device	rare	beneficial	Mithril pickaxe
.	6	8	food	extraterrestrial	beneficial	Loaf of bread with unusual tangy flavor. Unidentifiable grain. (permanent +1 CON)
.	7	13	food	rare	detrimental	Bowl of fine caviar. Anyone partaking in them will develop gills, webbed feet, transforming fully into a Mackrel-man in the course of a month
.	8	21	food	alien	beneficial	Cheetos from http://www.scp-wiki.net/scp-261. Can charm people/monsters at-will for 1d12 hours
.	9	34	text	extraterrestrial	detrimental	Stone slab with strange symbols/writings on it. For each day spent studying it, (INT)% chance of going permanently insane, otherwise, (2xINT)% chance of learning a random spell(regardless of class)
.	10	55	device	alien	detrimental	Device of Rods, Wheels(Masks of Nyarlathotep)
.	11	89	adventuring equipment	extraterrestrial	detrimental	Shiny Ray Gun. Explodes as grenade upon pressing trigger in high-O2 atmosphere.
.	12	144	creature	alien	beneficial	Friendly, Super-Intelligent gas creature. Can creep through any crack. Takes 1 day to begin learning basic terrestrial words.
.	13	233	device	alien	detrimental	Dark-Vision glasses. Also shows another dimention. 10% chance of losing insanity point for each 10 minutes of use
.	14	377	device	extraterrestrial	detrimental	Collapsable space-ship. Pressing a button will cause it to launch, stopping on the first planet it hits. Cannot be aimed--virtually no chance of ever returning.
.	15	610	text	extraterrestrial	detrimental	Silver-inked religious scroll. Meditation on indeciferable text will result in contact with Chaos Patron http://monstersandmanuals.blogspot.co.il/2010/02/chaos-patrons-revisited.html
.	16	1597	device	alien	beneficial	Tactical Helmet- improved initiative, trap-finding, ranged weapon accuracy, etc
.	17	2584	creature	other-dimensional	detrimental	Vampire mist
.	18	4181	text	other-dimensional	detrimental	Liquid symbols, float in air, dissappear within 3 rounds. Highly acidic.
.	19	6765	device	other-dimensional	detrimental	Ball of anihilation- any matter it touches is sucked-in forever
.	20	10946	drink	other-dimensional	detrimental	Second <Unknown> item from http://www.scp-wiki.net/scp-261

And let's say the players screw-up and put in an invalid number of gold coins...

2, 10, 82, 2- so as soon as the players open the box, a sulfurous liquid begins shooting out in a powerful stream.  It is acid and the one opening the box must save vs breath weapons or be splashed.  The room and dungeon will begin to fill-up with acid, up to 820,000 liters!