Vortex Key

The Vortex Keys were used in Pre-corruption times to open small bridges between words. During the corruption, the keys were used to close off vertexes and bridges up and down the chain. The technology and its original users were almost completely destroyed with the rest of Siv'ia. 
The technology was rediscovered by the children of Heaven. They have since been using them to slowly reopen Siv'ia's connection to the rest of the The Infinite Chain. This has been a covert operation in action since the Second Faerie Civil War ended. 
The goal is to reopen the connections slowly, to give both Siv'ia and the worlds below it a chance to get used to the shift in magic levels. This is in contrast to the sudden and mass shutting off that happened during the Corruption, which left Siv'ia under full blast of corrupted magic, and striped all worlds below of most or all of their magic in an instant.

Utility

The Keys are used to open bridges in the Infinite Chain. These can be as simple as a scrying pool or portal, or they can traffic magic, energy, and life to different worlds. Bridges are a unique being made kind of vortex which can be made against the flow of the Chain.

Access & Availability

Vortex Keys were rare and expensive to produce and power. As such, they were usually only available to the wealthy, or those whose jobs revolved around the use of the keys.
Now, only select children of Heaven know they exist, and even fewer are allowed to access them. The demi-deities carry out their operations in secret, and with the utmost responsibility.

Complexity

Vortex keys are incredibly complex techomagical objects. The slightest imbalance in the delicate machinery or the magic powering it can have catastrophic effects. As such, these items must be handled with the utmost care.

Discovery

Vortex Keys were first discovered elsewhere in the Infinite Chain, but spread quickly to the sentient life on Siv'ia. They were rediscovered by Isis Heaven, Morrigan Moon, Vivieno Moon, and Hades Vanessa. Further advancement in the technologies have been made by Thoth Moon and Quetzalcoatl Heaven.