This would be Lucifer in his true form... It doesn't look quite as impressive as Gabriel's but don't be deceived, they are almost the same, power wise.
Lucifer didn't gain his power until he fell, when his Holy Medallion cracked. Inside, he found, is a void of nothingness, that he can use to obliterate any threat. He uses his two halo's as a targeting system, and if you are unlucky enough to be within that small area, you will be sucked into the void.
Once there, you are basically reduced to nothing.
He doesn't like to use it, being as cheerful of a guy as he is, but the fact that he can, and will, if he needs to usually keeps threats at bay and people under his control.