Classic:

Creepers are now faster than normal and can give you the wither effect or kill you without even blowing up. the player has less health and burns in daylight and gets hurt in water but luckily you start with a leather cap but you still have to worry about water (just use a boat).

You are able to ride players in multiplayer (which i was gonna remove but the beta testers wanted me to keep it because it was funny). 

 almost every peaceful mob attacks the player except (wolfs, parrots, cats, and the new 1.17 mobs) ender pearls now explode (does this make blast protection more useful idk try it out yourself) 

i changed the main heart and absorption heart's texture so yeah i think it looks nice and i switched the textures to most of the ores back to their old texture and switched them so your gonna get confused on which ore is which. why did i do this? Well i thought the extremely fast creepers and small bats weren't enough to deal with in caves 

V 1.04: Updated the glowsquid and goats so they can attack the player

Reborn:

Basically you dead mode but with new items and mobs

there’s 5 new ore endite and 4 crystal ore plus a ingot that you can craft

use the crystals to craft the rainbow matter to craft 4 powered swords

the Sword of agility, the Sword of speed, the Sword of strength, and the Sword of defense

You dont need to credit me but please dont take my addon and put it on any other site or steal my addon and claim it as yours

thanks to the beta testers 
Sponeguy
and Sufferingkoala
Sufferingkoala's yt is here:  https://www.youtube.com/channel/UCyadt9nwE2AMuVyDRPgLY6w
Sponeguys’s yt is here: 

anyways have fun