It is in ORAS doubles list in format list in Pokemon showdown.
Rules Doubles format Every battle must include at least one dragon typed Pokemon or a Pokemon that can Mega evolve into a Dragon type (ie. Mega Charizard X) Mythics and Legendaries are allowed. This includes box legends and event Pokemon but only two per team. All Pokemon above level 50 will be set to level 50 for the tournament.
Pretty much a doubles battle that requires you to have atleast 1 dragon type Pokemon.
Also is a ORAS global link tournament where all who qualify will receive a Snow Warning Amaura.
Source: http://3ds.pokemon-gl.com/information/c60a5fbf-eab3-4f2d-9823-6ed7aa441cd1