Mini Avatars, generally referred to as "Mini-me" by their creators, are independent AIs used by people on the Of Empathy to preform various tasks without keeping the creator occupied.
Being AIs, they appear somewhat sentient, if not very intelligent or independent from their creators. They seem capable of any computer-related task, from database searches to advanced hacking. Likewise, they've proven capable of defending systems very efficiently, with Loeb's avatar easily fending of The Engineer's until the latter was upgraded.
Several characters have expressed a desire to themselves own an avatar, but the process of creating one has not yet been brought up. However, the only people to successfully do so to date are the Engineer and Loeb, the former being very skilled with computers, and the latter being moderately skilled and having very high admin privileges. They have not demonstrated any initiative or similarly independent thought, only following direct orders.
First appearing near the midway point of the core overload arc, it was called upon by it's creator to locate the appropriate hatch for Ener, Maddox and Ka-ley to travel through. Later, during the invasion of the core, it was tasked with disposing of Loeb's avatar in order for the Engineer to hack the doors. Initially, it was clearly outmatched by it's foe, until the Engineer upgraded it with the ability to duplicate in the millions. After some initial confusion, Loeb's avatar was easily vanquished, allowing the invasion of the core to proceed.
Appearing just before the final phase of the core overload arc, Loeb's avatar prevented the Engineer from hacking the doors to the control room, and defeated an atttack from the Engineer's avatar. In response, the Engineer created several million duplicates of his avatar, whereupon it quickly destroyed Loeb's.