Megiddo

Megiddo (神之怒) is Physics Magic used by Rimuru Tempest to gather ten thousand Souls for his Harvest Festival.

Abilities
This magic uses Spirit Magic to create small water droplets shaped by Water Elementals to create lenses that focus light into laser beams that are deadly to even someone like Folgen and Razen. Smaller water droplets are then used as mirrors to redirect the lasers toward the targets.

This process is very energy efficient as the attack that ends up striking the target itself uses no Magicules, Natural Energy, or Spiritrons, and any anti-magic barriers are entirely useless against the beams.

Weaknesses

 * It can only be used at daytime. (Before Raphael)
 * Scattering fine particles like dust or sand can impede or negate the attack.

Argos
Utilizing the same principle, Rimuru created the large scale surveillance system Argos (神之瞳). By deploying huge water lenses near the stratosphere, a magnified view of the target destination can be reflected to the control room, creating detail-rich video of the place.

Taking a page out of Moss’ book, Rimuru sent out a herd of tiny slimes split from himself, using them as a medium to activate the magic on site. All clones are connected to his main body through ‘Spatial Domination’, allowing for an instant data link and thus zero-latency streaming. The clones were too tiny to act autonomously, which had the added benefit of requiring no magicules so long as Rimuru didn’t consciously act on them.

The feed to the monitor was highly accurate after being processed by Raphael. A close-up view of whatever distant area could be enjoyed from the warmth of the Control Room. Moreover, Megiddo can be activated in the place shown on-screen. Utilizing a system with multiple lenses deployed in different time zone, Megiddo could even be fired at night by reflecting beams of light from one lens to another removing previous weakness.

Megiddo - Revised
Rimuru remodeled Megiddo in the How to Spend a Certain Vacation to bring to life fictional techniques from the manga – the 'Beast Magic' Koan-Yaa (光牙) and Chinku (鏡蟲).

Rimuru summons a powerful laser beam seemingly from his palm, but in actuality it's from the thin spatial distortion in front of the palm connecting his location to the giant water lenses in the stratosphere focusing the sunlight. The beam aims straight for its target at the speed of light, generating the afterimage of a three-headed dragon. Through the use of lenses created by a Water Elemental mimicking 'Chinku', the trajectory of the light can be freely adjusted by being bounced off multiple reflective surfaces. The beam of light is cloaked in Demon Lord's Haki to enhance its power and to deliver damage beyond just the physical body.

Trivia

 * Rimuru gained the inspiration for this magic from Hinata's Disintegration Magic.
 * The name of the Magic, "Megiddo," is the Hebrew word for, as well as the name of a place in Israel called , which is the prophesized location of the final battle between good and evil.
 * The sunlight power density is about 1400W/m2. To reach the power of industrial metal laser cutter i.e. around 5000W, the main lenses focusing sunlight need to be at least 3.57m2 in surface area or 2.14m in diameter, assuming no energy were lost. Therefore, the rendition in anime is somewhat accurate.
 * In That Time I Got Reincarnated as a Slime: Isekai Memories, the "Rimuru Tempest [Chancellor of Tempest]" unit uses this as a Secret Skill. Strangely enough, the English naming originally used direct translation rather than the top naming.
 * In Last Cloudia, Rimuru uses this as one of his Abilities.
 * In Seven Deadly Sins: Grand Cross, "「Octagram」 Demon Lord Rimuru Tempest" unit uses this as his ultimate move that inflicts damage on all enemies and applies an Abyss buff effect that inflicts after damage when your turn ends with a buff that has the unit taking 50% less damage for 2 turns.