some recipes for items, and also items core to progression do not have a recipe book entry, this will be fixed within the new few updates
each Layer will now have new cave biomes, And the nether will have new biomes as well.
Giant diamond caves will contain giant crystals made of a new block, Crystal Diamond Block. Crystal Diamond Block will be purely decorational to avoid destroying the rarity of diamonds as a whole. the same can be said about the Giant Ruby Caves, which will contain Crystal Ruby Block for the same reasons.
Geodes will now come in multiple Crystal Types, they are as follows:
All types have a chance at spawning, though Amethyst will be the most common.
each new biome will have new mobs.
frostmites
frostmites are small little bugs that spawn in groups. Frostmites attack via jumping at the player, dealing a small amount of damage as well as inflicting slowness. Another thing to note is when a frostmite dies, it will explode into an icy mist, dealing damage and slowness.
Dulfrog
Dulfrogs are large amphibian creatures that are related to frogs. These larger guys will pop out of the Dulmud, and attempt to bite the player, peircing and ignoring half of your armor.
the Dulfrog will also swallow fish, frogs, axolotls, and even items. Despite them posing a huge danger, you will be safe outside of the Grotto’s water. When killed, the Dullow will drop all the items it had swallowed.
Whisps
Whisps are ghosts that populate the Soul Sand Valleys. While seemingly harmless, the will teleport behind you and shoot soul fire balls, taking away oxygen and setting you on fire.
Dulfins
Dulfins are are small, blind fish that spawn in Dulmud Grottos, and are the main food source for the Dulfrogs that populate the waters. these fish are edible (you need to cook them lest you want blindness) and will allow you to regain some oxygen. the fish also have a unique behavior of jumping out of the water.
Chilled
Literally just a Husk but blue and icy and gives slowness instead of hunger. they will also take some oxygen from you when you get hit.
Frost Weaver
Frost Weavers are Frost spiders, and will wait patiently in powder snow for a player to come nearby. As a player comes nearby, they will jump out of the powder snow to attack. The Frost Weavers’s attack inflicts slowness and frostbite I
Dune Weaver
Dune Weavers are Spiders for sandy, arid biomes. dune weavers will wait patiently in the sand, only attack when the player is within 4 blocks away from it. the Dune Weaver inflict blindness.
chokepoint biomes are biomes that will have a increasing multiplier on oxygen loss (1.5x). For example, an ashy biome will be considered a chokepoint biome.
certain biomes will have a decreasing multiplier on oxygen loss (0.75x). An example of a biome with this modifier would be the Lush Cave.
new blocks will be added in caves that will create areas where you will slowly regain oxygen, or decrease oxygen loss further.
Each layer will now be sized based on how close they are to the surface, with Dolomite being 64 blocks, Cragstone being 80, Igniside and Rimestone being 128 blocks, and StarStone being 160. (Deepslate may be decreased to ~40 blocks, but this is undetermined ATM.)
you will no longer be able to sleep inside of caves below y=0 UNLESS you are in a Respir biome
Layers will now be more balanced when it comes to oxygen loss.
new potions effects will be added, and the potion of Oxygen Efficacy will get a new name and be remade.
potion of Hypoxia (3 levels, harmful) increased Oxygen loss multiplier (0.1x up to 0.6x extra loss) lasts for 100 ticks (5 seconds) at min level and up to 400 ticks (20 seconds) at max level.
potion of Rebreathing (3 levels, beneficial) decreased Oxygen loss multiplier (0.05x up to 0.5x less loss) lasts for 1200 ticks (1 minute) at min level and up to 3600 ticks (3 minutes) at max level
Frostbite (effect, 3 levels, harmful) deals 3 damage every 30 ticks at level 1 deals 3 damage every 25 ticks at level 2 deals 3 damage every 20 ticks at level 3 lasts for 240 ticks (12 seconds)
New spider types will be added. the only vanilla biomes that will be affected by this are deserts and mesas.
Deep mineshafts will be reworked to be hardcoded, so that the structure is more flexible with cave generation.
various new structures will be added. Some biomes with new structures will be as follows:
Parrots will now be poisoned if the oxygen loss multipler is >2x. this will also grant an achievement, ‘Canary In A Coal Mine’
More oxygen gaining items will be added, and the Base Item will be remade to be more flexible for use with other items. an item for storing extra oxygen will also be added.
Certain enemies will now drop oxygen bubbles, which are sort of like experience orbs but for regaining oxygen instead.