An Idea for a large mineshaft like structures that can be found when delving deep within caves in the form of Crypts, Found at Lake Cavern Level with creepy ambience and Trapped Loot Rooms.

Ideas for Crypt Loot Rooms

• A square room where a pedestal lies in the middle with a item of value on it, When the item is taken it will cause the door behind you to lock and the ceiling to slowly lower to crush you, To avoid this you must place a false idol in its place.

• A square room with caskets in alcoves in the walls and a pedestal in the middle with and item of value, When the item is taken the caskets open to release enemies and the door locks until they are killed. This could also be made with different settings lets say instead of caskets there's cauldrons for ShallowBreath's or Burrows for Crypt Crawlers.

• A Large Room with broken column's of varying size with ambient light shining on an item of extreme value on a pedestal in the center of the room like a life crystal, Once the item has been picked up the room would slowly fill with stagnant water and the player would have to parkour their way out. (Bit iffy on this one)

New Enemy Concept (Tarantula)

• Terrifying 2 block tall BetweenLands take on the standard spider, Spawning in caves deep underground you could make this thing move terrifying actually climbing on walls, Moving in a at first slow manner but able to move at fast unsettling speeds.

Could drop

• Giant Tarantula Legs that could be cooked and eaten like Delicacies in Cambodia or ground up to always give, (Muscle), (Earth), (Form) and (Mind)

• Tarantula Eggs, Could be cooked and eaten or used to grow spiders that would get bigger over a long period of time, You can also use them to get more spider eggs, Or they could just lay them with out your knowing and cause an infestation. Achievement Idea (Exotic House Pet)

Cave Event/Set Pieces

You could give the Standard Caverns layer a couple of minor not well noticeable set piece structures in the form of seemingly normal cave generations with traps a couple ideas I had where.

• What if when walking by a seemingly Unsuspecting hole in the Cavern wall, Chiromaw's Burst out of it and fly overhead before targeting you.

• When looking through the caves you could find a drop off point that goes far down, When you get close a Tarantula would climb up to the platform you are on and scare the player with its sheer size.

Concepts and Mechanics (Canary in the Coal Mine)

Noxious Gas may appear in caves some might be harmless others might be poisonous the threat level increases the deeper you go into caves, Most harmful gasses would only appear near pots of chance, May tie into herblore possibly representing elements, Gasses can be detected by using a canary the canary will freak out if near gas and allow the player to see the blocks covered in gas

Creature (Canary)
A Bird found in the BetweenLands can be used to detect poison while in caves , It could maybe have the same decaying affect on its sprite that the Lurker and the Chiromaw have.

Types of Gasses

(Flammable Gas)
Ignitable will cause a explosion of fire if set ablaze that will kill anything inside.

(Poisonous Gas)
Causes Nausea when in radius for to long followed by degradation of health that ramps up over time.

That's All
Sorry I know its long just wanted to get my ideas out there I hope they help you make this amazing mod.