A Collab, small, and AI-helped drop. Z + K collabed on a lot, so there will be no credit for any idea other than just Z + K.
Haunted Hallow biome, harvesting Candy Corn, feed Candy Corn to Hallowed Maw. Lightless mob. This stuff (Hallowed Maw, candy corn, haunted hallow, and lightless) is moved from Addon Concepts
Abyssal Forest: Spawns a bunch of hostile mobs, when the player walks in the light level becomes 0. Any light source block/item that is attempted to be placed down will just not place down and return to the player's inventory. There are ambient sounds that sound like hostile mobs only slightly distorted. The player is almost completely unable to see. Walk very carefully, because chasms like to spawn all over the biome. Logs: Black with grey accents. Leaves: Very dark purple. Spawns Zombies, Skeletons, Zombie Horses, Skeleton Horses, Spiders, Cave Spiders, Creepers, Witches, Zombie Villagers, and Slimes, as well as two new tameable mobs (one acts as a light source under certain conditions, another attacks hostile mobs) and a new hostile mob. Phantoms can also spawn here even if the player has slept recently. Can hold the Dark Den structure, which is full of loot but also lots of spawners.
Spectral Chasm: Holds Phantoms, Slimes, and two new hostile mobs as well as a new tameable mob. Also has a variant of phantoms and wraiths. Holds lots of Candy harvest spots. Candy is used for taming the new tameable mobs, or giving the player who eats it up to three effects at once. There are 50 different effect candies, and 4 different taming candies.
Tameable mobs: Light Source, Hostile Attacker, Spectral Chasm tameable mob, Hallowed Maw
Haunted Hallow: A cave biome that holds Candy Corn crops and also Hallowed Maws. There is also a new mob: the Lightless, which is similar to the Creaking, as it has a power source, but this power source cannot be destroyed. The only thing that can defeat it is running until it runs out of power, which it will recharge for 5 minutes. Also very dark but not as dark as the Abyssal Forest. Spawns a lot of Endermen.
Haunted Forms of mobs like Soul/Enchanted mobs from MCD. Maybe haunted trials too?