Drone

Drone is creature type that refers to simple, immature, or artificial lifeforms that perform tedious and menial work.

Mirrodin
Drones were living yet artificial beings created by the Vedalken of Mirrodin as guards, sentries, and shock troops. Though most likely self-aware, they lacked free-will and were the mute, unquestioning slaves of the Vedalken.

There were two varieties of drones: The land-bound Wanderguard Sentry patrol the entrances and byways of Lumengrid, using their psychic abilities to scan visitors' minds for unwelcome thoughts. They were tall, squat humanoids with bulbous metallic bodies sprouting spindly limbs, no neck, and a small head with huge unblinking eyes.

More common were the Hoverguard Observer, similar in appearance to wanderguards, but sprouting enormous gas-filled sacs from their backs that afforded them lighter-than-air flight. Most hoverguards lacked hands, instead, they have long metallic blades jutting from their wrists. Hoverguards doubled as sentries and taskmasters, the low hum of their inner workings a constant reminder to Lumengrid's Neurok slaves that they were under constant surveillance.

During the war against New Phyrexia, the Mirran resistance used hoverguards as Mirran Spy against their Phyrexian enemies.

Zendikar
Eldrazi Drones are a class of Eldrazi that are aligned with colored mana were first printed in Rise of the Eldrazi. Many of these Eldrazi Drones, as well as some spells, produce Eldrazi Spawn creature tokens. These 0/1 colorless creatures can be sacrificed to add —perfect for casting those enormous Eldrazi.

The Eldrazi Drones of Battle for Zendikar, though requiring colored mana to cast, have devoid and are therefore colorless. Some produce Eldrazi Scion creature tokens. These 1/1 colorless creatures can also be sacrificed to add.

Other
In addition to the drones created by the Vedalken and the Eldrazi, there were castes or specialized forms of spikes and viscerids known as "drones" as well.