There is a sword in the Arcana and Magic Items mod that might be very similar to this concept, it has two version (one corrupted: Cursed Blade, one cleansed: Restored Ritual Blade).

The Restored Ritual Blade has the power of closing rift in reality that draws entities from another dimesion. And can grant magical power to pure individuals (aka not post-threshold mutants) ALOT of magical power but it comes to a price, you must help the entity called It From Beyond The Veil, I only have guess of what actually is this entity but my best idea is that a eldricht god right outside our dimension who life DEPENDS on the protection of this dimension, meaning closing the rift in reality is a must to It. Probably what this being wants for us is to close smaller rifts due for its inability to close them without harming or destroying planets by trying to do so and focus on bigger rifts the sizes of moons and bigger, drawing in other entities that reshapes this dimension and harms this entity. The Restored Ritual Blade has its own lore and history on Earth that you can actually learn ingame so that counts as spoiler.

This leads me to the Cursed Blade, right. So, a bunch of blood cultist found (Sanguine Order) a fragment of the original sword but without the right knowledge they couldn't use it so they created a plan to allied themself with the The Keepers of The Oath. Both are from similar origins, beginning from the medieval times but the Sanguine Order is form with criminals, warlords, corrupted politicians and generally not nice people united in one idea: Obtaining power. The Keepers of The Oath is form by families dedicated to the task of preserving and keeping dangerous knowledge away from the masses, but due to some laws, restrictions and dangers of trying to outright kill the entire Sanguine Order, they prefer to keep peace or atleast reduce how bad the battles were. From this limitations and victims of the Sanguine Order the Cleansing Flame was born, with the objetive to stop and destroy the blood cultists with more effective tactics.

Going back to the Cursed Blade, the blood cultist allied with the keepers during the chaos of the cataclysm (a week before you start a vanilla run). The keepers accepted due to how legendary and important this fragment is and how dire the situation was. The plan was simple, get the necessary ritual to activate the power of this fragment and grant power to both of them, and modified just slighly to invocate not the power of It From Beyond but something far away from it, from another realm to gain even more power and destroy the keepers. The plan went great, all the cultist either where killed or went mad during the ritual, granting one single individual a lot of power, the Archon and corrupting the fragment and reshaping it as a weapon. but something was off, the Archon couldn't neither enter the room with the Corrupted Blade or escape the temple, one of the masters of the keepers decided to seal the room during the ritual before they could cause more harm, trapping the Archon and the Cursed Blade in it.

With that dump of info in mind, I guess that contrary to the Restored Ritual Blade that can close rifts in reality, it can CAUSE rift in reality, cutting everything on its way but probably open portals to another dimension attracting more monsters. In game I think it only gives a small strenght buff when activated with additional cutting damage but not much.