A Haunted Biome. Complete with broken portals, graves, dead bushes, pumpkins, mycelium, and a dead tree (hopefully it’d have a face without using a pumpkin, a rare decorative block that works as regular haunted wood, which would be a grayer shade as planks). Even in daytime, zombies, skeletons, and spiders are immune to sun effects (and the sky is a darker tint) Vines and mushrooms grow in the biome, as well as witch huts. Witches appear in the biome, and it has a new melee-based mob (or I have an idea for one) ghost mobs, they’re typically neutral, but when attacked can ONLY be hurt by enchanted tools, but punching them will make them hostile regardless. They act similar to villagers except they slightly hover (similar to ghasts in motion, except basically ground bound.)
Leaves on haunted trees are always a purple shade (used wool to emulate) and not all haunted trees would have leaves. Planted grass in the biome is swampy green or black, even. Cobwebs can appear in small numbers on the surface, and graves can be cracked brick or mossy cracked brick, or stone slabs. Bats can appear all day, outside.
The biome would be about as rare as a mushroom biome (and would be the hostile counterpart, basically.) Small numbers of mossy cobble can appear, and the place would be pretty dangerous all day, making for a “venture if you dare” atmosphere. Those who want the rarest wood, and rare resources would be up for an all day mob challenge. (Possibly chests with items could fill the graves. Including things like zombie and skeleton heads, roses, bones, swords, and armor, as well as dirt or rotting flesh). There would be traditional mines, but like mentioned above, spiders (and cave spiders, where relevant) skeletons and zombies and witches can spawn within, even when lit, making it a pretty dangerous area. Possibly with a higher chance of dungeons (with a slightly increased chance of Record 11, and chances of Haunted Saplings, as they would be rare since it kind of fits the area) and abandoned mines, and cobweb appearing throughout caves in small numbers.
Hostile mobs appear more often with armor and weapons, but don’t drop them too often.
A new type of structure as well: Abandoned villages. Structures in disrepair, zombie villagers, chests with very scarce resources, maybe even endermen actively disassembling the area when you enter. Water is only one or two blocks deep and isn’t very common. Farms are only half hoed and have no crops planted.
If you went here on hardcore, you’d be either REALLY bold, or trying to leave as soon as you could. Other than bats (and ghosts) no neutral mobs would spawn at any time.
Could either be an island biome similar to Mushroom Island, or be a rare biome appearing on other continents, at least 500 blocks from spawn.
Anyone else like this idea? Feel free to tell me other ideas that could be added.