• Add a new boss named GRUG (of course) that does different attacks to the player and any entity that damages it.
• Adds a new mob named Baby that spawns after Grug reaches a certain low health.  All this mob does is run really fast and damage the player.
• Adds a new The Egg Item that allows the user to gain extra hearts permanently.  You can also give an Egg to your TAMED dog, giving it extra health as well.  The Egg is dropped from Grug 100% of the time.
• Adds a new Shades item that, when equipped as a helmet, blinds the player that is using it.  Because it's just wood.  You can also craft the Shades as shown below.  For clarity, any planks will do, naturally spawning in the overworld and but not cherry grove. :
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• Adds a new Rug item that, when equipped as a helmet, does nothing except make you look like an ugly lady.  You can craft it as well, with pretty much any carpet as shown below. :
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• And lastly, Grug has a 50/50 chance of dropping either the rug, or the shades.

Now, all jokes aside, Grug is extreemeeely tough.  The gear I recommend at least to beat him would be netherite, but you can go diamond if you're like that.