As permanents are so much better than spells these days Austere Command is one of the most comfortable mass removal spells you can hope to play
Any set released after March 30th will also be legal 2 weeks after the release date
That makes this an automatic inclusion all decks that are trying to play good old fashioned Magic in the correct colors, running the gamut from control to pure burn
While its a relief to know you defeated them, theres still two issues: The fact that this individual could come back, since you told Professor Hibiki that it sped away after your encounter, and the fact that you seem to be his voice trailed off as he searched for a suitable word
Its one of the Power Nine, a set of cards that has been banned from most formats of competitive play for their overwhelming power.
Exile all opponents' graveyards, then create X 0/1 black Thrull creature tokens, where X is the greatest power among creature cards exiled this way