Automata (singular form: automaton) are semi-sentient robot-like creatures that spawn underground from culverts, randomly in caves, and also sometimes from behind mined silver crates. They come in many different sizes and shapes, but almost always have brass fittings and parts. They appear to have cobbled themselves together from the remains of other machines, as their components (e.g., conveyors and weapons) may sometimes be seen elsewhere in the game.
There are many different varieties and sizes of automata, most of which have weapons. Some automata cause damage upon contact, others will shoot at you, and a few cause no damage at all but will merely try to shove you around a little. If you're within visual range of any automaton equipped with a weapon, it will shoot at you.
Some automata are able to fly, while others are ground-based. Flying automata seem to have movement mechanics similar to brains, meaning, once they catch sight of you, they will attempt to move closer and will stay close, shooting at you, until you either kill them, run away, or block their ability to see you.
In general, ground-based automata will walk in one direction until they hit an obstacle, then simply turn around and begin walking in the other direction, regardless of the player's position. They will still shoot at you if they can, but they don't pursue you like flying automata do. Ground-based automata are able to jump up over two-block high barriers, but cannot scale a wall or obstruction 3 blocks high. They climb stairs and can traverse various configurations of diagonally-placed blocks. However, like nearly all other walking mobs, automata will skip over a one-block-wide vertical chute in a flat surface.
Some automata are harder to kill than others. Often they will spew broken parts as they take damage. The larger the automaton, the more damage it will deal to the player and the harder it is to kill. Energy cannons and acid cannons are often cited as the best weapons against this mob.
Killing a small automaton will drop scrap metal into your inventory. Larger automata often drop canisters.
XP from killing automata ranges from +3 for the little ones up to +30 for the largest ones.
The component parts of any given automaton are determined randomly at the time it spawns.