What are minions?

The lore does not matter.

On a side note, they are artificially created cat girls who weren't good enough to become call girls.

In the old lore, they were mindless puppets created by the summoners to control in the fields of Justice.

... However, in the new lore, we dont have a lot of information about them, specially considering that the game is not canon and they are not fighting in the Fields of Justice.

Anyways... Riot released a game called "Mechs vs Minions", in that game, they seem to be sentient beings that live in the Magma Chamber near Bandle City or something like that.

Who do you think repairs all the towers inhibs and what not after a game? Who do you think tells the Dragons and Harolds when to spawn? Who do you think takes care of all the plants and jungle monsters so they don't die? Who do you think cleans the river and takes care of the forest?

Thats right.. Minions. SO A LITTLE BIT MORE RESPEC IF I MAY ASK!

Jokes aside these guys have no natural enemy dude there are like millions and billions of minions just plunging into their death by running into towers and champions like there is no tomorrow. Either all of them are masochists or they are like pandas and don't know it better....

Also the sex drive of these guys must be insane to keep that quota up for 10 years

To the question on what exactly they are uhhhh.... The caster minions look like Veigar so there might be a connection

They are powerful ancient gods who challenge mortals to combat. (Yes, each minion is an individual ancient diety with its own history, set of powers and personality.) When you kill them, it's an illusion one of them cast on you to hide that they killed you even before the first wave spawned.

Each of them is powered and controlled by the minds of LCS live audiences.

Xayah says they are magically animated sacks of cloth.

they come from the nexus