Use this to survive an eradication power from Atriox or keep your army alive until your team mates can show up etc. If you use stasis on your own units then they can’t move or attack either but also become invincible. Time to escape or time to attack turrets first or destroy a base and they have no choice but to watch.
Basically if you use stasis on enemies their units can’t move or attack but cannot be harmed. He has regular stasis and also mass stasis which is just stasis but on a larger scale. The Arbiter is definitely more focused on his stasis leader powers.