[Celestial Guardian]

the functionis tow fold.

1) to protect your firewarriors/pathfinders by putting another target in the way to force a priority check to shoot the unit

2) to protect your firewarriors/pathfinders by maing the unit unavaible for assault.

As Ikaurs pointed out,m if used correctly with backup (often putting tow units close enough to each other will give more firepower to your units and double the space around to your units (triple if both fishes are turned sideways)) the effects can be quite devastating to even the mighty space marines.

The priority tests are nice when forced, but are able to be passed most of the time. The real benefit is getting as many shoots off as you can and keeping your opponent from assaulting you.