This is another multidirectional pun. First, in German, the word for ‘council chamber’ is Ratskammer. Second, it’s an anagram of Star Chamber, a special civil and criminal court in England. Created by Henry VII in 1487, abolished by the Long Parliament in 1641 following abuses under James I and Charles I. The court took its name from a star-shaped decoration in the ceiling.
The decoration in the ceiling of the Rats Chamber — a group of rats with their tails tied together — is called a rat king. According to Maarten ’t Hart, in Rats (translated from the Dutch), some 57 rat kings have been found since the 17th century, although several are of dubious authenticity. They are often found alive, and can contain as few as three or as many as 32 members, although seven is the commonest number. Members are of both sexes, and almost always of the same age group, which may be young or adult. Rat kings are generally formed of black rats (Rattus rattus), although there is one occurrence of field rats (found in Java) and several of squirrels. No-one knows quite why they form, although one theory is that black rats (which have longer and more pliable tails than other breeds) get something sticky on their tails, and get tangled up when they groom each other, or while playing or fighting.
Apparently, a modern artist decided to make a work of art depicting a rat-king, and even put it on the internet. See Katharina Fritsch: Rat-King (Rattenkoenig), 1993 http://www.diacenter.org/exhibs/fritsch/ratking (which also has an essay on the rat king through history).