Astral Link

Astral Link is a certain type of object that recently became as an important factor of ongoing (while still crawling) industrial revolution in Imperium of Karadia. It works by binding an area (called Domain) with the Dark, not unlike magical anomalies, but in a safe and stable way. Astral Links - and its Domain - can be directly controlled by their owners, which can be compared to having a small magical anomaly at your disposal.
They are an artificial, weakened version of Astral Core, achieved via very advanced techmaturgy. Can be produced in Imperium of Karadia of today, although not in great numbers due to costs and required resources. Their exact capabilities depend on the skill of their creators, the resources that were available to them, and plain old economic calculation, as noone creates more complicated (and expensive) astral link than he needs.
Cheaper links serve as a form of a security for some installation - for example a mage secret laboratory on outskirts of civilization, dungeons of some castle (or even castle as a whole), mine etc. - from intruders. They allow to easily rebuild damages by reverting the place to its earlier, 'ideal' form using ambient mana from the air. They can also be used to anchor certain daemons into their Domain, making it easy for them to manifest. They can even replenish the air and keep the average level of lighting. It still requires a competent magician to make any changes, and does not allow to use magic to somehow influence the environment, like the Astral Core's allow.
Their biggest advantage? They can not only connect the area with the Dark, but also weaken such connection, locally stabilizing the magical anomalies and allowing the location of permanent hideouts. A notable part of produced links ends up there.
More advanced models allow the expansion of Domain, can possess a graphical 'interface' that can recognize certain people as administrators (they don't even have to be magic users to administrate it), and can power up things like short distance teleports, adjustments to environment like building tunnels from the interface (it is still slow and requires aether to power up such changes, making workers at least equally profitable).
Domain does not has to be beneath the ground, but in most cases it is. Mostly because it makes it easier to construct entirety without having to bother with paying the architect to plan it without the risk of collapse. It is also easier to 'direct' the intruder when you wish. While they all differ in terms of view, they tend to have a decently sized mana crystal (or a whole array of them) that serve as an anchors for the spells from which the Link as a whole is created.

Item type

Jewelry / Valuable

Raw materials & Components

At least one very big Mana Crystal, sometimes several smaller ones plus lesser ingredients for enchantment proccess and aether both to power up the machine as a whole (not to mention the magician enchanting it).