Homunculus

Homunculus (Latin for "little human") is a blue creature type used for cards that depict a artificially made, but sentient and living, miniature humans. These creatures are used for menial or dangerous tasks. A well-made homunculus grooms the mind of its master, pruning the thoughts that lead to madness. Few loredelvers survive the study of the infinite without one. Many homunculi just have one cyclopic eye (Oculus, Riddlekeeper)

The first creature to bear the type was Bonded Fetch in Future Sight, though the Sneaky Homunculus from Nemesis was later issued errata to become an Homunculus in addition to an Illusion.

Esper

Esper, one of the five Shards of Alara is inhabited by blue-skinned homunculi. The mage of Esper measure their wealth and status by the number of these creature in their retinues (Court Homunculus).

Innistrad

The homunculi of Innistrad are based on upon the hunchbacked assistants of mad scientists or vampires in old Horror films (Stitcher's Apprentice).

Illusions

Some homunculi are just the stuff of dreams and lack the appropiate Homunculus subtype (Hazy Homunculus).