Elderspell

The Elderspell is a spell that Nicol Bolas used during the War of the Spark to harvest planeswalker's sparks. It would grant him "ultimate power" and godhood. The origin of the spell is unknown, but Dack Fayden recognized it as primal, elder magic.

Description
Bolas cast the Elderspell to grow his own power by absorbing the sparks, right after the invasion of Ravnica by the Dreadhorde. It granted the Eternals the ability to distinguish planeswalkers from the crowd. The spark harvesting, as performed by the Eternals, was lethal. All they needed to do was to establish a solid grip, and all the moisture in the victim's body was drained. The Eternal would absorb the planeswalker's life force right out of his body until it glowed from within their lazotep shell, glowing brightly enough to create—or at least highlight—cracks in their lazotep coating. The Eternal would then burst into flames from the inside out. The stolen spark would rocket into the air, shooting like a purple comet toward Nicol Bolas and leaving the burned-out Eternal behind. The God-Eternals could steal sparks without dying in the process.

The Elderspell created a vast storm of magic, dropping all of Ravnica into an artificial night punctuated by the stolen Planeswalker Sparks that rocketed like comets toward Bolas and the mystic Spirit-Gem floating between his horns, feeding the dragon and his power. Bolas grew in god-like stature with every new acquisition.

The Elderspell made the Eternals especially deadly to planeswalkers since it enabled the Eternals to kill planeswalkers with merely a touch; all it took was a few seconds of physical contact for an Eternal to harvest the spark from a planeswalker's body. However, Davriel Cane was able to fight off an Eternal by stealing the Elderspell from its mind (which may enable him to cast it himself).

Hundreds of planeswalkers were killed by Eternals and had their sparks harvested, fueling Bolas' power. This made Bolas nearly invulnerable, to the point where only the Gods of Amonkhet and their weapons could hurt him. It is implied that Blackblade would have been able to hurt him too, had he not specifically taken precautions against the weapon in advance. The Elderspell also greatly enhanced his magical power, to the point where he could repel the God-Eternals Oketra and Bontu, and later obliterate Oketra altogether, with merely a thought. It apparently enhanced his physical strength too, as a simple strike from his wing was enough to send Niv-Mizzet flying miles through the air. While empowered by the Elderspell, Bolas could seemingly alter the fabric of reality around him at will; after being impaled by Hazoret's spear, he was surprised to find that he couldn't simply will it out of existence (which was only the case because it was imbued with a fraction of his own power).

The effects of the Elderspell were reversed when the God-Eternal Bontu bit Bolas, claiming all the sparks (including Bolas' own). After this, Bontu exploded in shards due to the sheer abundance of magical energy coursing through her body. All the stolen sparks flew into the air, dispersing into the Aether.

Victims
Named:
 * Domri Rade
 * Khazi
 * Dack Fayden
 * Nicol Bolas

Unnamed:
 * A lime-green Viashino planeswalker
 * Two Vedalken planeswalkers
 * A female Elf planeswalker
 * A four-armed Ogre planeswalker
 * A short green-haired male Human planeswalker
 * An elderly female Human planeswalker
 * A teenage Human planeswalker
 * A bald female Human planeswalker with metal-casting powers
 * A tall Elf planeswalker wearing a long white hooded cloak
 * A dark-haired Human planeswalker wearing a red scarf (shown on The Elderspell)
 * A blonde-haired Human planeswalker wearing a padded armor vest (shown on Spark Reaper)
 * Hundreds of other planeswalkers

Trivia
During Dakkon Blackblade's confrontation with Chromium Rhuell the former describes the latter as "pulling his spark" when he is being subdued. It is unclear if there is any sort of connection between this and the elderspell.