Swooping evils are flying hostile mobs that spawns at high altitudes. It can be quite dangerous, as it is attracted to insomnia — it feeds on players's brains who haven't slept for many days - and its skin has the ability to deflect some spells.
Swooping evils spawn at night, or at any time during a thunderstorm; high above players that have not slept for at least 3 days. Swooping evils will spawn more often the longer a player has gone without sleep.
For swooping evils to successfully spawn, the player in question must be above sea level and not have a block above its head which blocks light in any way.
Once the conditions are right, a pack of 1–4 swooping evils attempts to spawn above the player every 1–2 minutes.
Swooping evils drop 0–1 powdered moonstone when killed by the player.