Ziggurat sphere

A ziggurat sphere, siphon, or spinning orb of death is a component of the Briarwoods' ritual to revive Vecna. Though they share some properties with the D&D 5e Sphere of Annihilation, these siphons are a distinct homebrew by Matthew Mercer.

Two spheres have been encountered by Vox Machina; one beneath Whitestone and one in Marquet. A third exists, but its location is unknown.

Appearance
The orb is a small, black sphere, about the size of a dime or a marble, which hovers a little above the ground. On close inspection, it appears to be spinning very rapidly.

When manipulated by Delilah, the sphere turned bright white. In a vision from Sarenrae, Pike was able to see it as a doorway surrounded by spinning blades.

Properties
While in siphon mode, the orb creates an area of antimagic within a certain radius of itself. Spells and magic items have no effect within this radius, though they still consume spell slots. Sustained magical effects, such as Feeblemind, are resumed once moved away from the sphere's influence.

Anything that touches the orb is sucked in and takes a moderate amount of force damage. However, by using a special amulet, Delilah's cultists were able to travel through the spheres into the Shadowfell.

Vox Machina had chased Delilah Briarwood into the ziggurat beneath Whitestone, hoping to prevent her from completing some unknown ritual. Vex arrived in time to see Delilah read a scroll, gash her wrist, and spatter blood over a black orb resting in the center of the ziggurat.

The orb rose into the air, started to spin, and shrank to the size of a dime. Delilah seemed to think the ritual had not worked, saying, "No! It can't be too soon! Please!" As this happened, all magical effects in the area suddenly ended, including Vex'ahlia's Fly spell, and nobody was able to cast any spells or use any potions near the orb.

Once Delilah had been subdued, Keyleth attempted to hit the orb with a piece of residuum. The piece was destroyed as it touched the orb, and Keyleth narrowly avoided having her hand sucked in, taking significant damage. The party then decided they were not equipped to deal with the orb.

The party interrogated Cassandra about the orb, but she was only able to say it was part of a ritual for The Whispered One, Vecna. Keeper Yennen offered to go look at the orb. The party sent word to Eskil Ryndarien and Allura Vysoren to come investigate it as well.

Gilmore said that the "spinning black orb of death" sounded like a Sphere of Annihilation, but that those were generally a little larger. Vex speculated that Delilah might have meant for it to be larger.

Allura reported that the orb's anti-magical properties made it difficult to investigate, and that she had only been able to confirm its destructive effect on anything thrown into it. She was hoping to bring her research to a library, although the Cobalt Reserve had just been destroyed.

Returning to Whitestone, the party conferred with Eskil Ryndarien on his research. He had little to add beyond what Allura had discussed, but did mention that the orb appeared to be acting as a siphon.

Allura, having returned from her salvage mission to the Cobalt Reserve, made a report on her, Gilmore, and Eskil's research progress. She revealed the following:
 * The orb was not exactly destroying the objects passed through it, but rather breaking them down and siphoning their magical energy elsewhere.
 * Siphons like this had been used in the First War to craft powerful magical items like the Vestiges, though most such siphons were thought destroyed or inert.
 * The siphon must have another end somewhere, but it could be on another plane of existence.
 * No attempts to send scrying objects or other such items through the orb had succeeded, and the researchers were running out of things to try without traveling to more places.

Vax'ildan used the orb's anti-magic field to escape from a cursed Robe of Flaying.

Zahra mentioned that it was fun throwing things into the orb and watching them go away.

The Council of Whitestone began using the ziggurat as their war room, relying on the orb's anti-magic field to prevent illusion magic and Scrying.

While Vex and Percy were visiting the ziggurat, Vex had the idea to fire an Oracle Arrow through the siphon. With a rather good shot, she succeeded. Through the arrow, she saw the twin orb at the other end (which was not producing an anti-magic field) and a broken, grey landscape with a black tower at the center, which Allura was then able to identify as the Shadowfell. Allura promised to set off for Vasselheim the next day to learn more about where exactly the tower could be.

Lionel Gayheart approached Vox Machina in Whitestone to report a second orb in a ziggurat in Marquet.

Vox Machina set off with Lionel to investigate the second ziggurat. Inside, they found Delilah Briarwood, resurrected, with a second orb just like the one below Whitestone. She used an amulet to control the orb, turning it from black to white. As long as the orb remained white, its usual anti-magic field was gone.

Delilah eventually toggled the orb back. She and her cultists stepped through it into the Shadowfell, revealing its portal-like ability for the first time. Pike prayed to Sarenrae and was given a vision of the orb as a doorway into the Shadowfell, surrounded by a hundred spinning razors. Upon interrogating one of the cultists, she learned that the cultists' amulets allowed them to pass through the orb safely.

Donning the cultists' necklaces, Vox Machina were able to pass through the sphere beneath Whitestone while taking only a moderate amount of damage. The sphere's portal brought them to the Shadowfell, outside the city of Thar Amphala. There, they saw the shattered remnants of objects from Allura, Eskil, and Gilmore's experiments.

Vex was able to see a faint, purplish strand of ley energy reaching from the siphon to the tower at the center of Thar Amphala. She also saw two more strands from the tower down into other places across the city, implying that a total of three spheres existed throughout the world.

As Vax and Scanlan circled the Tower of Entropis, they saw a nexus of pulsing energy at the convergence of the three strands from the siphons. The energy suddenly seemed to pulse, sending out a shockwave, and a group of people at the top of the tower fell dead. Thereupon, the strands from the siphons disappeared. It was not long after this that Vecna made his debut at the top of tower.