Well I played both Mass Effects and the first one twice. I'm fairly safe in my knowledge of lore of it I feel, but I don't remember anything off-hand. In-game knowledge pretty much tells you everything you need to know. I'll look some of it up, maybe it'll jog my memory.
Their psionic powers don't seem nearly as strong as SC or SW though and Halo has none of that.
Was looking at Halo Array article. Nothing says it can't be fired the moment they are activated. There also used to be 12, now there are 7.