Emperor is a climbing card game (in the mold of President, Tien Len, The Big Two, Tichu, The Great Dalmuti, etc.) that is playable with two regular card decks shuffled together. It was designed as a climbing game primarily for 6+ people (though rule variants permit 4-5 people to play as well).
The game allows singletons, sets (pairs, three of a kind, etc.), runs, and multi-runs (consecutive pairs, consecutive triples, etc.) as legal plays, which must then be followed by a play of that same type and of the same length, except in the case of special combinations known as "bombs." Several jokers are used as wild cards. Between rounds there is a unique redistribution phase in which all players discard a card face down; these are shuffled and dealt randomly back, one to each player.
Advanced rules allow for "calling a coup" in which one player names a calling card; the first person to play this calling card is the coup caller's partner. The coup succeeds if either player goes out first. A coup partnership receives a bonus or penalty depending on whether the coup succeeds or fails.
Other advanced rules allow for "class division" rounds in which face cards ("noble cards") cannot appear in combination with number cards ("commoner cards"), and in which there is "taxation" between rounds instead of redistribution (during taxation losers give winners their highest card). Further successful coups cause the game to toggle back and forth between such a class division round and the initial "class harmony" style of round, in which there are no restrictions on the play of face cards and there is "redistribution" between rounds.