Thundurus

As you go through certain Ultra Wormholes while traveling through Ultra Space, you will sometimes land in an area where, as you land, you are told there is a strong presence coming from the area - this is a clue that a Legendary Pokemon is there. All Wormhole Legendary Pokemon can be found in there Shiny Forms, and after catching all the Legendary Pokemon of a specific location in the Ultra Space Wilds, you will be notified that the presence there is now gone.

By traveling through a Red Ultra Wormhole, you sometimes will be able to find and thus battle the Legendary Pokemon Thundurus. Thundurus is an Electric / Flying Type Pokemon, and it will be found at Level 60 knowing the moves of Discharge, Crunch, Charge, and Nasty Plot.