Some hardcore survival with mobs way more powerfull than in the vanilla version with a lot of tech and content.

Every vanilla monsters are upgraded in the modpack, they will break doors, torchs and your plants.

Zombies and Skeletons now also have gear, swords, armor, etc... some will even be bosses with much more health.

And a whole lot of new creatures, both hostile and friendly, have also been added.

The Overworld has been greatly improved with new biomes, lots of new structures and dungeons.
New dimensions have been added Midnight, Twilight and Betweenlands, but both the Nether and Ender have also been enhanced with new biomes, monsters and resources.

And of course in addition to all these world improvements a lot of content has been added, new armor, weapons, firearms, and equipment of all kinds.

Mod list:

Multi Mob Library (by Daveyx0)
Serene Seasons (by TheAdubbz)
PneumaticCraft: Repressurized (by desht_08)
Parasites Addon : OverLast (by acherlins)
RFTools Power (by McJty)
Primitive Mobs (by Daveyx0)
Thermal Cultivation (by TeamCoFH)
Better Third Person (by Socolio)
Shadowfacts' Forgelin (by ShadowfactsDev)
Rough Mobs 2 (by Lellson8)
Eyes in the Darkness (by gigaherz)
Dynamic Lights (by atomicstrykergrumpy)
Thermal Foundation (by TeamCoFH)
Immersive Craft (by McJty)
Redstone Flux (by TeamCoFH)
CoFH Core (by TeamCoFH)
Thermal Expansion (by TeamCoFH)
Craftable Slime Balls (by distressedstick)
Simply Light (by Flanks255)
RFTools Control (by McJty)
CoFH World (by TeamCoFH)
Placebo (by Shadows_of_Fire)
iChunUtil (by ohaiiChun)
Mob Dismemberment (by ohaiiChun)
Bookshelf (by DarkhaxDev)
Better Foliage (by octarine_noise)
MeanMobs (by GatoGamer887)
RFTools (by McJty)
NetherEx (by LogicTechCorp)
MineTraps (by XxRexRaptorxX)
Thermal Dynamics (by TeamCoFH)
AI Improvements (by QueenOfMissiles)
Surge (by DarkhaxDev)
Tough As Nails (by TheAdubbz)
Spartan Weaponry (by ObliviousSpartan)
The Midnight (by cipher_zero_x)
Phosphor (Forge) (by jellysquid3_)
Draconic Evolution (by brandon3055)
Carry On (by Tschipp)
Solar Flux Reborn (by Zeitheron)
Brandon's Core (by brandon3055)
Immersive Engineering (by BluSunrize)
Additional Structures (by XxRexRaptorxX)
ConnectedTexturesMod (by tterrag1098)
Crafting Tweaks (by BlayTheNinth)
YUNG's Better Caves (Forge) (by YUNGNICKYOUNG)
Familiar Fauna (by Forstride)
McJtyLib (by McJty)
Traveler's Backpack (by Tiviacz1337)
Mantle (by mDiyo)
Trinkets and Baubles (by XzeroAir)
Inventory Tweaks [1.12 only] (by JimeoWan)
MrCrayfish's Furniture Mod (by MrCrayfish)
Sulfur And Potassium - More Gunpowder (by BR4NDER5)
Obfuscate (by MrCrayfish)
Corail Tombstone (by Corail_31)
Scape and Run: Parasites Addon by NoCube (by nocubeyt)
Biomes O' Plenty (by Forstride)
Improved Backpacks (by DreenDexTwitch)
Chunk Animator (by Lumien231)
FallingTree (Forge&Fabric) (by RakSrinaNa)
YUNG's Better Mineshafts (Forge) (by YUNGNICKYOUNG)
Immersive Petroleum (by Flaxbeard)
SwingThroughGrass (by exidex)
AttributeFix (by DarkhaxDev)
OreLib (by OreCruncher)
FastWorkbench (by Shadows_of_Fire)
AppleSkin (by squeek502)
Fast Leaf Decay (by olafskiii)
Iron Furnaces [FORGE] (by XenoMustache)
The Twilight Forest (by Benimatic)
Just Enough Items (JEI) (by mezz)
Baubles (by Azanor13)
TexFix (by Speiger)
BetterFps (by Guichaguri)
MrCrayfish's Gun Mod (by MrCrayfish)
Mowzie's Mobs (by bobmowzie)
LibraryEx (by LogicTechCorp)
Dynamic Trees - The Twilight Forest (by supermassimo0310)
Patchouli (by Vazkii)
Thermal Innovation (by TeamCoFH)
Artifacts (by ochotonida)
Applied Energistics 2 (by AlgorithmX2)
LLibrary (by mmdlexiconn)
Dynamic Trees - Biomes O' Plenty (by cadaverous_queen)
Performant (by someaddon)
Redstone Arsenal (by TeamCoFH)
Scape and Run: Monstress (by Dhanantry)
Chameleon (by Texelsaur)
Scape and Run: Parasites (by Dhanantry)
Dark Utilities (by DarkhaxDev)
CoroUtil (by Corosus)
Zombie Awareness (by Corosus)
Spartan Shields (by ObliviousSpartan)
CreativeCore (by CreativeMD)
Mouse Tweaks (by YaLTeR)
End: Reborn (by elecatron)
Storage Drawers (by Texelsaur)
Dynamic Surroundings (by OreCruncher)
Dynamic Trees (by ferreusveritas)
Clumps (by Jaredlll08)
Useful Slime (by MincraftEinstein)
[ANGRY PIXEL] The Betweenlands (by MrCompost)
Xaero's Minimap (by xaero96)
CodeChicken Lib 1.8.+ (by covers1624)
Roguelike Dungeons -- Fnar's Edition (by FnarDotTv)
Nature's Compass (by Chaosyr)
Tinkers Construct (by mDiyo)
Better Animals Plus (by cybercat5555)

La mort de ses morts là

[ANGRY PIXEL] The Betweenlands

Additional Structures

AI Improvements

AppleSkin

Applied Energistics 2

Artifacts

AttributeFix

Baubles

Better Animals Plus

Better Foliage

Better Third Person

BetterFps

Biomes O' Plenty

Bookshelf

Brandon's Core

Carry On

Chameleon

Chunk Animator

Clumps

CodeChicken Lib 1.8.+