Death Forest/Open Mob Arena Covering

[Wivren]

My request is to cover a large forest with a layer of blocks at max build height to create a massive area of darkness for mobs to spawn freely.

Center of the area is at roughly X6970, Y-2074.  Preferably the layer would be a circle of blocks centered on the previous coords, with a radius of 220 blocks, preferably black wool.

The eventual goal is for the area to have safe zone forts for players, mini-dungeons, riddles leading to hidden treasure caches, and mob spawners placed throughout, a sort of RPG open-world mob arena.

Below are pictures of the island where I am and the arena will be located, and a zoomed in shot of the forest

Edit: Just FYI, the massive block of dirt in the photos was a quick test I did to see if it would darken it well enough.  It did. >=)

[Migas]

A 220 block radius request is very big. Can you explain a little bit more your idea for the area, please?

[Wivren]

The idea is to recreate the "Forest of Doom" trope that crops up in a lot of fantasy MMOs and literature.  It would be open to any player, but recommended for a party of 3-4.  The layer of blocks at max height is needed to let spawners work in the open, also for an evil, (literally) dark atmosphere.  With mobs all the time, anyone will be welcome to use it as a mob arena, or grind for XP.

There will be a fort towards the north of the area which will be a small safe zone from the mobs.  People can come get food if they've run out, potions, just take a break.  A few of dungeons of varying difficulty will be scattered around the area, mostly with puzzle games like jumping, sharpshooting, or just a proper mini-mob arena.  Treasure caches with riddles to find them as well, changed and restocked once a month with prizes.

The whole point is to create a unique, communal area for people who might've gotten bored of building and pressing buttons on their auto farms.  It's meant to be fresh and challenging to even the most well equipped player.  I'll obviously need help putting it all together, but that's a separate issue from the world edit request.

[Migas]

It sounds like a great idea. However, there's some issues with the request, mainly that making a 220 radius circle in the sky means that lots of blocks will have their light blocked. Minecraft is very sensitive with blocks and having this whole area blocked from light at the height limit will easily crash the server.