In Finnish folklore, Ajatar (also known as Ajattara or Ajattaro) is an evil female spirit of the forest, “the devil of the woods”. She has many forms and depending on the description, she’s said to be a witch, a ghost, a snake or a dragon. Ajatar spreads diseases and plague and anyone who looks at her becomes sick. It was believed that Ajatar was the reason why people got lost in the woods and her name is probably derived from the Finnish word ajattaa; ‘to lead’, ‘to pursue’.
The scene begins with a wonderful soliloquy by the castle porter where he thinks to himself of "a man were porter of hell-gate, he should have plenty of turning a key" (2. 3.1-2). He then further speaks stating "i' the name of Beelzebub" basically saying that he serves the devil. unbeknownst to the porter this is dramatic irony as he is serving an insane murderer.