Seven Days At Sea: Shipwreck Compass, A System-Agnostic Magic Item

 Shipwreck Compass

Description:  A pocket-sized compass made of heavily verdigrised brass.  The pointer needle is rusted, and the face of the compass lacks the usual cardinal direction markings.  Basic magical examination reveals a strong aura of enchantment and divination magic tied to some form of seeking effect.  More advanced techniques will reveal the nature of its powers as below.

Powers:  Once briefly immersed in a body of liquid, the compass needle will infallibly point toward the nearest shipwreck within that body, be it a river, lake, swamp, sea or ocean.  Movement away from the direction indicated may change which shipwreck is nearest, resulting in the needle shifting to a new target.  This effect lasts until the compass is placed within a different body, which resets it to a new wreck.

The Shipwreck Compass will trigger when dipped in any "body" of liquid, including things like a mug of ale, a well, a millpond, or pool of lava (which may well destroy the item in the process, usual saving throws or damage resistances apply).  If there's no shipwreck within the liquid, the needle will spin wildly until reset.  The same "scrambled" result will occur 50% of the time if the compass is immersed near a boundary between two bodies of water, such as the mouth of river or a coastal swamp, and the other 50% of the time the compass will randomly "imprint" on one body or the other.  The compass performs normally even with underground rivers, pools, and seas, although navigating to a distant wreck is likely to be more difficult than on the surface. 

It is also possible to trigger the seeking function by briefly burying the Shipwreck Compass in a dried sea bed or similar geological formation.  The odds of finding a wreck are lower due to passage of time and they may well be buried deep below the surface.

In addition to its obvious utility in locating sunken treasure, the compass may also be helpful for avoiding dangerous reefs and shoals by using it to indicate what direction not to sail in.  This is somewhat unreliable unless one can be certain the nearest wreck lies on or near such a formation though.     

Possible Origins:  The first Shipwreck Compass was likely the product of some unknown mage from an undersea civilization, but land-dwelling artificers have gained access to the rituals and formulas required to create their own.

Complications:  Shipwreck Compasses are highly prized by seafaring treasure hunters, many of whom are noted for unscrupulous behavior.  Fakes are also fairly common on the marketplace, usually employing some form of concealed mechanical gimmickry to point the needle in a set direction.

There is also considerable danger involved in recovering sunken treasure, not least of which being the natives of the undersea world.  Many such creatures regard drowned riches as their own by right, and the use of old wrecks as lures for food, loot or slaves from the world above is not uncommon.

Design Commentary:  Starting a series of "aquatic adventure" themed posts this week with this.  These gadgets do have some utility for other milieus, although you'll want some fireproofing magic if you plan to trawl the Seas of Flame outside the City of Brass.