The Full Changelog for this update will be included in V1.4.3.1's Changelog, which should come out in 1-2 weeks (and will bring 1.21.5-8 up to date!). If you are curious about what was added/changed in this version, I suggest checking out the Discord Server!

Here are some brief snippits of what was added/changed:

• New Melee variant of the Bloodlink Sentry called the Bloodlink Piercer; it digs underground and pops up beside you, grabs you, and uses its head to drill into you
• New tier of Biome Mobs called the Abysmal Biome Mobs, which are another set of bosses
• Monarch (evolution of Emperor) will rapidly fire I-frame ignoring projectiles when at high health, but as its health decreases, it will use a wind gust attack instead with a gigantic aoe. When Below Half health, it will spawn Crimson Worms and Emperors, and will transfer any incoming damage onto any Crimson Worm or Emperor within a 64 block radius. When very low on health, Monarch will gain a Shadow-Dash ability, where it can accurately launch itself towards an enemy dealing high damage and breaking blocks in its path, and will spawn a very fragile shadow clone of itself in its original spot, which will perform the same attacks as Monarch at half the frequency
• Purified Mace has been buffed/reworked; While falling, right-clicking will teleport you partially back to your original height, and will store all your gained momentum, allowing for the mace to stack up a ton of damage. In addition, the Area Damage now linearly scales with the number of blocks fallen, instead of being fixed values.
• The infected Biome has recieved an overhaul to appearance. It should now be more aestetically pleasing, and now blocks such as dirt, wood, snow, ice, spruce leaves, etc. now get tinted a certain color when inside an infected area.
• Bloodlink Sentry now has new animations, and an altered appearance
• Decayed Bogged has been retextured to be more differentiable from Crimsonified Bogged
• Decayed and Crimsonified mobs now have their own unique spawn eggs instead of sharing a single one per mob type
• there is now a Crimson Curse Advancement Tree
• the Mass Threshold and Points system has been completely overhauled:

1. The Mass Threshold in EVERY Phase is now 1000, rather than being between 1000 and 8000
2. The Points needed for the infection to increase in Phase has also increased
   Phase 1: same (0-9 Points)
   Phase 2: 10-39 --> 10-99 Points
   Phase 3: 40-149 --> 100-749 Points
   Phase 4: 150-299 --> 750-1499 Points
   Phase 5: 300+ --> 1500+ Points
3. The system for Evolved Biome Mob-spawning is now done through the Mass Theshold system, meaning that Evolved mobs will no longer require a Stage 2 or 3 Bloodlink to spawn, but now, Primal Biome Mobs can be slain before they have the chance to evolve (Note that S2 and S3 Bloodlinks can still spawn Evolved mobs, but their chances have been reduced from 14.28 --> 5%, and 25 --> 10%, respectively
4. Crimson Siphoners and Crimson Blighters will now remove 5x as many points as they previously did, to make up for the Point system being so drastically reworked

• This project is now fully compatible with Spore Fungal Infection
• The Bloodlink Reinforcement system will no longer randomly cause world-ruining lag
• Nodes now take up less processing power, and as it currently stands, over 3000 can simultaniously exist without breaking the mod (prior to this update, if more than 500 Nodes were simultaniously loaded, they would cause the whole mod to break)