Every few hours the world might turn against you. Red sky, distorted sound, and enhanced monsters that hunt by sound. Sleeping won't skip it.
A Bloodmoon is a hostile night event. Each night has a 1 in 15 chance of being one, so it comes around every 15 hours or so. It's announced when it starts, and it's unmistakable.
Bloodmoons spawn enhanced variants of normal mobs. They're faster, stronger, and ignore the rules you usually rely on for safety.
Four flavours of enhanced mob spawn during Bloodmoons. Each takes a familiar mob and makes it scarier in a different way.
Quick, strong, poisonous melee.
Faster, hits harder, splits on death.
Volleys of poison arrows.
Small, fast, and silent.
Soul Torches are the Bloodmoon's counterweight. They are excellent base defence.
You can prepare for a Bloodmoon, but you can't outrun one. Stay home or stay quiet.