Stranglehold | Magic: The Gathering
Formats Stranglehold is Legal in
Official Oracle Text for Stranglehold
If an opponent would begin an extra turn, that player skips that turn instead.
Official Rulings for Stranglehold
9/22/2011 : If your opponent controls a Stranglehold and an effect says "Search your library . . . Then shuffle your library," the search effect fails, but you will still have to shuffle.
9/22/2011 : Since opponents can't search libraries, they won't be able to find any cards in a library. The effect applies to all opponents and all libraries, including your library. If a spell or ability's effect has other parts that don't depend on searching for or finding cards, they will still work normally.
9/22/2011 : Effects that tell an opponent to reveal cards from a library or look at cards from the top of a library will still work. Only effects that use the word "search" will fail.
9/22/2011 : An "extra turn" means a turn created by a spell or ability. It doesn't refer to a turn taken in a sanctioned tournament after the time limit for the round has expired.
9/22/2011 : If an opponent's extra turn is created while Stranglehold is on the battlefield, but Stranglehold leaves the battlefield before that turn would begin, that opponent takes the extra turn as normal.