This looks like it's new (did a search on it and since I'm a steam account I can't post this to the wiki) while working on a full tier run, I came across this. Had no idea what it was. While useless (it's currently on Aurora Isles, jelly farm 2 which is on the ruby sun gate... which is at a depth of 1) it's still interesting. it looks like it has a small laser that has sustaining damage when fired. It costs 5 energy to activate it. Here's pictures attached. the first one is in its deactivated state and the second one is in the activated one. It rotates around while activated scanning for enemies like a team fortress sentry.
http://cloud.steampowered.com/ugc/613846549860602733/4A6349CAABE00613BF1...
http://cloud.steampowered.com/ugc/613846549860599600/5250F8721BD7FC56F13...
now, as a "paste" in the steam browser these both work. but I'm not entirely sure if they will in a normal browser for normal people. so here's the link to the screenshots folder they're in.
http://steamcommunity.com/id/darth_ganon/screenshots/?tab=public&
edit: whoops. someone's already got a wiki on it. My bad.
It has been around for a long time, probably since the beginning of the game, it just doesn't appear randomly, only on some Aurora Isles levels at pre-defined locations.
It's not that useful, like mechaknights, because it costs energy and slimes are easy enough (there are only slimes where you see those turrets).