Aeon engineers have the ability to Sacrifice. They kill themselves in order to give an immediate energy boost to a construction. Each tier engineer gives a different amount, with Tier 1 giving the least amount of energy and Tier 3 giving the most. However, the Tier 1 engineers give a greater percentage of their original cost than the Tier 2, and Tier 3, which give a progressively lower percentage of original cost of the Engineer.

A pre-3254 exploit allowed Aeon players to pause upgrades on their commander, sacrifice one engineer, then unpause, resulting in an upgrade for the price of only one engineer. This was resolved in hotfix 1.1.3254.

Don't underestimate the power to finish a colossus or harbringer by ridding your unit population of those later hindrances referred to as T1 engineers. Sacrifice can be put to use immediately and gives you energy as well as mass, making it superior to reclaiming your outdated engineers. This also puts you in a unique position, if your opponent is foolish but aware of sacrifice, then you may damage a critical structure of his that he needs, like ACU or a factory. The foolish opponent could sacrifice your factions engineers and later remember he will need to capture them again to access aeon tech. This can be countered if they construct a factory, but you can get rid of it with a colossus or gunships and bombers.

Sacrifice can be a lifesaver for your ACU, especially if your ACU is being attacked by T3 bombers, as the engineers can heal the ACU between bombs while you wait for shields and AA to move in. You can also utilize this strategy: use a combat ACU to {with support} attack an outpost or base. The ACU can be covered with it's own shields and some mobile ones, and if there is light or no AA, you can send in transports to drop engineers, or SACU's to heal him.

Using 5-6 SACU's with both the sacrifice and the personal telporter upgrades, it is posable to insta build a Galactic Colossus ANYWHERE on the map, even within you enemy's base.  As demastrated by Chosen on a Gyle cast; here