Advent Weapon

Helps all friendly units fighting in that system. Use it before sending your fleet into a large battle, helps alot with shields and can make the difference between winning and loosing.

It's a culture thing...

It seems kind of weak compared to the TECs, for example. I had a player build two of those things, and he keeps killing my planet pop. ='(

The Deliverance Engine is a very effective weapon to support your fleet in a major battle. It spreads your culture in the grav well, which means the enemy gets denied his culture bonus, and you gain yours. In the case of vs Vasari, you gain 6% shield mitigation, and the Vasari player loses his 11% damage bonus. Pretty considerable!

In addition, the Engine drops allegiance of targeted hostile planets, and a few chained shots is enough to get a planet to rebel (obviously the closer to the homeworld the longer/more shots it takes due to max allegiance).