Nightmare
Nightmare is an extremely difficult survival world that uses the Extra Hard Mode plugin to add new challenges and game mechanics to Minecraft’s survival mode.
This world is invite only. Those who are invited must have first played in Darkness and have not had trouble following any of the server rules.
What you can expect from Nightmare:
Falling Blocks
Certain blocks such as dirt & cobblestone fall like sand, making digging and building structures much more difficult. Mining an ore block causes all adjacent stone blocks to turn into cobblestone. Falling blocks hinder your progress by getting in the way when you’re digging or potentially falling on top of and suffocating you.
Death Penalties
When you die, you will permanently lose some of the items in your inventory. And upon respawning, your health and hunger bars will only be partially refilled..
Debuffs
When taking damage, you get the slowness III debuff for a few seconds. In addition, monsters can give various effects such as blindness, hunger, and blank when they attack you.
Spelunking
Caves are some of the most dangerous places in nightmare. While spelunking, you will encounter enemies you’ve never seen in Minecraft before.
Cave-ins may also occur, as well as other unexpected events….
Torches cannot be placed below deep underground, so if you’re digging for diamonds be prepared to mine in the dark, or get clever with alternate light sources!
No rest for the weary
Beds cannot be used in Nightmare, meaning you cannot set your spawn point or skip the night.
Blight
Half of all planted crops will die, turning into dead bushes. Additionally, crops require natural sunlight to grow. They cannot be planted indoors or underground.
Infestation
Silverfish will be a nuisance while playing Nightmare, appearing when you least expect it.
Some mobs even spawn silverfish upon attacking.
And Much, Much More
This page only lists a small fraction of the dangers you will face in Nightmare.