Fierce
In Isaiah 19:4 and Deuteronomy 28:50, this signifies unmercifulness. (Arcana Coelestia 6667)
In Exodus 32:12, this signifies that the people turned away from things divine; for when wrath or anger is mentioned regarding the Lord, it signifies man turning away from God. (Arcana Coelestia 10431)
In Matthew 8:28, this signifies a demonic obsession by people who, in the world, had been in falsities from evil. (Apocalypse Explained 659[6]; True Christian Religion 405[3])
Arcana Coelestia # 6667
6667. 'With rigour' means without showing any mercy. This becomes clear without explanation, for those spoken of immediately above in 6666 have no mercy because they have no love of the neighbour, only self-love. Love of the neighbour which seems to be present among them is nothing else than self-love. For as long as another is favourably disposed towards them, that is, is on their side, they love him; but as long as he is not favourably disposed towards them or not on their side they reject him, and if previously their friend they hate him. Attitudes such as this lie concealed in self-love, though they do not reveal themselves in the world, only in the next life, where they burst out into the open. The reason why they burst out there is that there outward appearances are taken away; and when they are taken away, one sees what a person has been like inwardly.