An angel is a messenger of God. God can send out as many messengers as he needs. Evil Knievel probably needs more than one angel to help him jump the canyon. They come from special places like heaven or earth. Not in the way we think, but they do rest.
Angels are a pool of energy.
If they have so much energy they should not have to sleep. It is the presence of God himself, a gathering of God's people, a gathering of believers. It is the celebration of a tragedy, the death of Jesus on the cross. But anything that is God's plan cannot be a tragedy. We resolve it through faith.