Hiberian String

'Bounty hunters, eh? Well, for the bandits you get two gold apiece as was agreed on, and... hmmm... twenty gold for that rope if it is in one piece.'

Full Item Description
It is a rope, or string depending on its size. The only specialty are the black and green strings interwined through it, and an unusually complex weaving of the strings that compose it, both rarely noticed by the common user.

If recognized, it is called 'Hiberian String', 'Elven Rope', 'Nature's Pull', 'Druid's Hair', 'Eternal Rope' and a few other names.

Magical Properties
Surprise: It is stronger! A little stronger by itself, in a weak magical enviroment (the fantasy norm) it can carry double the weight than a comparable string or rope; channeling magic into it can make it hold even more.

Further, unless it is damaged or overloaded, the rope will not fray or tear, esentially lasting forever. (Unfortunately it is not immune to rats.)

If a simple Heat cantrip is used on the string, it will glow violet for a while, the intensity determining its quality. (Yes, it has even a minor resistance to heat; can withstand fire for a moment.)

Production and Use
Made by reclusive Elves even today, it is a fiercely guarded secret of the right combination of filaments, fibers, weaving techniques, and not to forget the right spell, all inherited from ages ago. With it, the magical elements are forged into symmetry with the rope's woven structure, able to channel weak currents of magic, thus giving it shape and purpose. The rope itself is not magical at all.

After the many years, there are several groups now with differing knowledge of the process, producing strings of different qualities. Still, the secret is unknown to the world at large, commanding outrageous prices for a usable piece of rope. There are many fakes as well so beware.

Barring whims of some monarchs, that equipped their flagships with this rope only, there was only one more consistent use across the ages: traps. A mechanism that has to last for ages, and protect the grave of a wealthy person, is best propelled by a Hiberian String. With some protection, it will catch your thief in five or five hundred years equally well.

History
The string was actually created by the Arascans, that have started with the very idea of researching semi-magical technologies. Due to an oversight of some long-forgotten magus, it has been mis-attributed to a completely different people, and the name stuck. History happens.

Summary
There are no real downsides to this item. It may be prohibitively expensive, or rarely have a strange reaction with potent magics, but that's it. Just a useful item.