The Swooping Evil is a blue-and-green winged magical creature. It looks like a cross between a reptile and an extremely large butterfly. When it is not flying with its spiked wings, the Swooping Evil shrinks into a green spiny cocoon.
It can be quite dangerous, as it is an encephalophage — it feeds on people's brains - and its skin has the ability to deflect at least some spells.

It secretes venom that, when properly diluted, can be used to erase bad memories. The Ministry Classification of the Swooping Evil is unknown.