Minions are magical constructs, summoned specifically for use in battle. Earliest recorded use of minions for battles was at the battle field known as Summoner's Rift, where ancient sides the Protectorate (Stag crest) and Magelord (Owl crest) summoners fought against each other.
The process of minions spawning needs constant and massive amount of magical energy to be sustained. Minions are not fully sentient beings, rather they are controlled by the summoners who use nexuses. The Nexus structure focuses enough magical energy from powerful crystals for sustained minion spawning and its destruction disrupts and stops the summoning magic.
There are many ways a minion body can be magically constructed, ranging from animated magic scrolls, animated sand, magically animated bolts of cloth, and even sound.
Necromancy is a minion summoning technique that uses dark magic to reanimate corpses. Like ordinary minions they are not fully sentient and are completely controlled by the user who summoned them. Most known practitioners of necromancy come from the Shadow Isles.
Also, while not magically constructed, living minions share many traits with magically constructed minions. Voidlings summoned through (ZzRot Portal) portals are controlled by those who have necessary magical power to use them; one of such known persons is Malzahar. A Celestial Being known as Bard is frequently followed by minion-like spirits known as Meeps that aid him in his tasks (though they are more like companions than outright minions).