I am up for multis :3
>>34410532I don't know if the thread multi "meta" has developed in my absence, but there's no rules really. Generally if you can bring it to Battle Tree, you can bring it in multis. People (rightfully) get annoyed if they bring regular Pokemon and are up against Mewtwo and Mega Rayquaza.
Here are the some of the teams I have used, if you want a reference point.