The Magnesis Rune is obtained in the Oman Au Shrine at the Great Plateau. The Magnesis Rune allows Link to harness magnetic energy to lift and carry metallic objects into the air effortlessly, which can then be moved and placed elsewhere. When the Rune is activated, red grid lines cover Link's immediate surroundings. Objects in that area that can be picked up will have a red filter, and will turn yellow as the Rune's cursor moves over them, signifying that they can be selected. Once lifted, Link can manipulate the object either by moving it in the air, dropping it, or pushing or pulling it. This can also be used to hurt enemies through various methods, such as dropping heavy metal boxes on top of them.
Metallic Treasure Chests can be picked up using the Magnesis Rune—this can be used to move Treasure Chests that are normally out of Link's reach.
In Hyrule Warriors: Age of Calamity, Magnesis is used as a combat ability used by all Warriors. Located on the R Button wheel along with its sibling Runes and tied to the B Button while holding R, Magnesis can be used in a variety of ways.
When it is prompted, Magnesis is used to counter a monster (mainly a giant Bokoblin or Moblin) or a human enemy like Master Kohga throwing a metallic (enough) weapon by grabbing it with magnetic energy and sending it right back at them to damage/expose their Weak Point Gauge, stunning them in the process.
Alternatively, Magnesis can be used by picking up metal crates to make them be used as improvised weapons. Otherwise, Magnesis must be used against a sizable group of enemies so that it can successfully use magnetized weapons from enemies that is picked up by Magnesis.
Once Magnesis is used in a combat manner, it puts the entire R Button wheel on a cooldown for every playable Warrior that is on the field, so the cooldown cannot be circumvented by switching characters. Completing the "Shocking Fear" Quest and the postgame-exclusive Quest "Zappy 'n' Bouncy" lowers the cooldown after using Magnesis.
As Zelda's first weapon class is Sheikah Slates, Magnesis is incorporated into her moveset. As it still counts as Magnesis without using the actual Magnesis prompt by using the R Button, Zelda's first two Strong II Combo strings can be used in place of a Magnesis counter.
Can used to substitute for Magnesis counter prompt
Y X X
Can used to substitute for Magnesis counter prompt
Y X X X
Creates a metal cart with Zelda standing inside it, which rockets forward
All of the Warriors in Hyrule Warriors: Age of Calamity have their unique spin on using the Magnesis Rune power:
Link: Link uses Magnesis much like how he did in Breath of the Wild. He then walks forward with a rotating ball of magnetized weapons.
Impa: If not used to counter, Impa creates a greatsword made of various weapons and shields to extend the length of her kodachi, and slashes with it once, then raises it for a powerful overhead strike.
Zelda: The way Zelda uses Magnesis depends of her weapon:
Sheikah Slate: Zelda makes a floating ball of magnetized weapons that follows her. She can then detonate it like a giant magnetized frag grenade.
If used as part of a counter prompt, the ball will then fly towards the stunned enemy.
Bow of Light: Zelda creates a burst of light magic that, when successful, creates an ball of light magic and magnetic energy.
Mipha: Mipha picks up weapons and small monsters alike into a rotating ball of magnetism. If used as a counter prompt, she sends it flying back with a swing of her weapon.
Daruk: Daruk creates a ball of magnetized weapons, then hops into a spinning front flip, slamming the ball into the ground.
Revali: Revali combines his Gale with the Magnesis Rune to create an electromagnetic tornado with weapons and shields.
Urbosa: Urbosa gathers a collection of magnetized weapons that spins like a buzzsaw, then uses her Fury as a lightning rod to extend her attack.
Hestu: Hestu creates a rotating ball of magnetized weapons and shields, then sends it at the target.
Sidon: Sidon creates a fishing pole that creates a ball of magnetized weapons and shields. He then "fights" with it, then sends him up in the air to potentially paraglide off of it.
Yunobo: Yunobo creates a ball of magnetized weapons, then begins spinning in a counter-clockwise manner before throwing it.
Teba: Teba creates a electromagnetic tornado of magnetized weapons that buffer the opponents. He can then move around halfway into it.
Riju: Riju creates a ball of electromagnetic energy, then has it explode with lightning.
Master Kohga: Kohga creates a controllable ball of magnetized weapons that soon explodes.
King Rhoam: King Rhoam creates a ball of magnetized weapons that then explodes.
Great Fairies: The Great Fairies creates a ball of magnetized weapons, then withdraws into their flower with the ball. They then shoot out three balls of magnetized weapons.
Monk Maz Koshia: Monk Maz creates a ball of magnetized weapons, then shoots it forward.
Terrako: Terrako creates a tiltable ball of magnetized weapons, then shoots it forward.
Calamity Ganon: Calamity Ganon creates a ball of magnetized weapons, then summons a pair of spikes that frames the ball that slams into the ground, exploding it with the power of Thunderblight Ganon.
The word magnesis is a contraction/portmanteau of the word "magnetism", which comes from the Ancient Greek magnítis líthos (μαγνήτης λίθος) which means "lodestone from the region of Magnesia", and "kinesis" (κίνησις, kínisis), which is Ancient Greek for "motion".
↑ 1.01.11.2"Magnesis Manipulate metallic objects using magnetism. Grab on to metallic objects using the magnetic energy that pours forth from the Magnesis rune. Objects held in the magnetic snare can belifted up and moved freely." — Runes (Breath of the Wild)