A barely understood phenomena. These points in space and time cause a wide range of anomalies, bending or sometimes even breaking the known laws of the universe. They can also act as tunnels, or highways across the multiverse enabling easy traversal between dimensions.
Some have hypothesized that they form when two or more timelines across the multiverse briefly touch, causing conflicts within the very fabric of reality leading to these zones where anything seems possible.
Across the multiverse there exists an infinity of timelines. These alternate universes are not static, they fluctuate like a waves. They also don't all flow in the same direction, leading to some strands of the tapestry hitting each other.
Nexus points are spots in space and time where a large amount of timelines touch each other. Experts have determined that there exists an unseen force that causes these threads to attract each other, leading to a compounding effect where once a critical mass has been reached a nexus forms where more and more threads get pulled in.
This puts an extreme amount of stress on the hosting timeline as it's own laws of existence get constantly altered and eventually the timeline risks getting completely unraveled.
Such worlds are also frequently a constant battlefield as many multiversal organizations use this opportunity to exploit the Rifts, as well as expand their power and influence since not these places can also act as multiversal highways allowing those with the tech necessary to go as they please and reach many other places across the multiverse.
Another theory put forth by experts that helps explorers determine how close are different timelines to each other is the existence of echoes. These can manifest in a multitude of ways, but they tend to find themselves in the collective consciousness of the locals.
Books, movies, stories told around a campfire, tropes and clichés are all signs which one could use to determine the distance between their current timeline and other ones.
While Rifts are a natural occurring phenomenon there are ways, highly dangerous and hard to achieve, to artificially create them. Scholars call them Rift Tears, as the very fabric that separates timelines is torn asunder and the points in space-time are overlapped creating portals that anyone can travel through - even those who normally would die during multiversal travel.
The primary danger in creating these tears is that there are few ways to stop them and even fewer to reverse them. Entire universes were unraveled because too many tears ripped them to shreds.
Sealing such wounds requires for the two timelines to be properly disconnected and then only powerful Time Lords can attempt to reverse the damage suffered.
A person who can tap into the mystical power is called a sorcerer. Magic is purely a mental exercise. It requires no specific hand gestures, no specific phrases etc. It appears to be an expression of the user. As such each individual's magic prowess takes different shapes.
Magic is the 5th Universal Force. It is alien in nature, as it entered the universe through a Rift. Those who can properly tap into it are also Riftborn even if there are no physical differences between them and regular people.
Magic is an exploration of inner space, it gives people great amount of power and turns their minds into living weapons.
While most magic requires a power source to draw it's magic, there are those who are born with innate power sources. The Tower of Magic calls them Primals, as they're able to channel spells much more easily, have an instinctual ability to control magical energies and require no outside power to use basic spells - unlike others.
Primals usually manage to achieve quite a lot if their talent is honed, they represent most of the people that attend the Tower as well.
Considered one of the most rare metals in the multiverse, it's origins have been lost to time. A byproduct of Rifts, it is highly coveted by all for it's ability to absorb and redirect kinetic energy. Silvery in coloration, it doesn't stain and can cut through anything.
Attempts at synthesizing it have failed, the only way to procure it is to harvest and process the faint traces that sometimes get left behind at Rift sites.
When a new timeline is created six fragments are brought into existence by processes that are poorly understood. These shards contain incredible amounts of power:
These shards lose their potency outside of their native timeline, but inside they become some of the most powerful artifacts coveted by most individuals or groups. Locating and retrieving them is hard, as when the universe expands they are also affected and could theoretically be anywhere within the vastness of space.
There are various methods for detecting them, from magical rituals to powerful sensors and probes that can detect the anomalies that form around each specific object. Areas of instability and erratic change, large vast empty regions of the universe where nothing seems to be able to survive, civilizations becoming hive-minds, space-matter anomalies, massive planetary sized graveyards or temporal abnormalities. These are only some examples, but each piece if left without any containment over time distorts the cosmos around it in quite noticeable ways.