User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-131.239.63.5-20150812215612/@comment-24834479-20150818235821

She meant that there were billions of other gods, not just God alone. What people do as ghostsaffects where they go in their afterlife. There are not different afterlives for people depending on their religion. Humans either go to Heaven, Hell, or remain in the Veil when they die. All monsters can use summoning spells as long as it is using external magic. Those two tricksters have not been talked about by the writers, so no, they don't currently exist within the show. They are head-cannon books which a lot of people use to interperate the show, but they aren't 100% canon. (Please don't rush me for these answers, I wait for my friend to reply to me, and don't want to rush her.)