AbyssalCraft is a mod centered around exploration, but with a growing magic influence. Another thing that has been getting more focus is influences from the works of H.P Lovecraft, adding even more evil to that which is already in the mod.
Enough about that, let's dig into the mod! The first thing you need in order to get started is a Necronomicon, crafted like in the picture below:

Most (if not all) information about things from the mod can be found in the Necronomicon. Apart from being a guide book to the mod, the Necronomicon is also serves as a catalyst for performing rituals.
Going in a bit more on the mod, AbyssalCraft features a collection of dimensions known as The Abyss (the world of the dead, split into several layers, where each layer is a dimension). The dimensions (4 in total, whereas the fourth is a bit of an extension to the third) are:

• The Abyssal Wasteland (quite green, inhabited by various undead beings, among them the vanilla zombies and skeletons, then new mobs added in the mod).
  
• The Dreadlands (red, a place crawling with nameless mutated beings that may or may not have been a normal creature sometime in the past).
  
• Omothol (the realm of J'zahar, a dimension consisting of floating islands with a city built upon them, this is where you encounter the final boss).
  
• The Dark Realm (dark place beneath Omothol, populated by living shadows).
  

In order to reach the various dimensions, one must obtain Gateway Keys (items capable of placing down portals when used).

Apart from traveling between dimensions, there's also a pitch of magic, in the form of rituals consisting of an altar and pedestals which you place offerings on. There's several different types of rituals, among them rituals where you create items, rituals where you infuse items (turn one item into a different, or simply "upgrade" the item). There's also rituals where you can summon things (the first boss is summoned through such a ritual), and rituals where you can inflict potion effects on nearby entities. If you want to create your own type of ritual, there's an API for that, and if you simply want to add your own creation/infusion ritual, that can either be done through the API, or with MineTweaker (the add-on modAbyssalCraft Integration has MineTweaker compatibility).

In addition to the rituals, there's also a new form of energy used in order to perform the rituals. This energy is called Potential Energy, and can be obtained through a few methods (this is being expanded).
Along with all of this is also a lot of new blocks (among them 5 new types of stone, 15 new ores, 2 new types of trees), new items (among them 4 new materials to make tools and armor from, 8 new armor sets, a bunch of new food items).

Enough about quantities of things, the Overworld has also received new content, including 6 new biomes:

• The Darklands (more "evil" version of a forest/plains blend, purple/indigo grass, contains Darkstone and a new type of tree, Abyssalnite can be found here)
  
• Darklands Plains (plains version of the Darklands biome, has close to no trees)
  
• Darklands Forest (forest version of the Darklands biome, has a lot more trees)
  
• Darklands Highland (extreme hills version of the Darklands biome, more elevated terrain, not that many trees)
  
• Darklands Mountains (mountains composed of Darkstone)
  
• Coralium Infested Swamp (a teal/turquoise swamp, has Liquid Antimatter underground, along with the large quantity of Coralium, which is more common here than in ordinary swamps or other water-based biomes)
  

Since I haven't mentioned the mobs, let me go over a few of them. There's the Depths Ghoul and Abyssal Zombie(both undead, found in Darklands biomes, swamps, or very commonly in the Abyssal Wasteland), evil counterparts of vanilla animals (Pigs, Cows, Chickens), Living Shadows (Shadow Creature/Monster/Beast, each one stronger than the former), and Lesser Shoggoths (if you're familiar with the works of H.P Lovecraft, these are smaller versions of those amorphous horrors). That's all the mobs found in the Overworld, whereas some can be found in the dimensions.

Want my mod in a modpack? Sure, go ahead, but follow these small steps, and you have my approval:
1. On the website where the modpack is, credit me and provide a link back to this page.
2. (optional) Send me a message or comment here that you made a modpack, and provide a link to it.

Follow those 2 steps, and you have my approval of including my mod in your modpack.

Modpacks where AbyssalCraft is featured:

Things you are not allowed to do regarding modpacks:

For adventure/RPG styled modpacks

Redistributing my mod is only allowed if you do it the right way, which is the following:
1. You are not allowed to make ANY revenue off of my material (use any form of ad mirror, force any form of payment prior to download)
2. You provide a link back to this page (notifying visitors that this is the original source of the mod)
3. You redirect ANY download to this page (or use MY Adf.ly links, which can be found at the download section)
4. You use your own pictures, or the ones found on my threads or on my wiki (in which case you don't watermark them are your own, since they are not yours AT ALL)
5. Credit ME, since I'm the reason this mod even exists.
6. Personally PM me asking if you could post my mod on your website, while providing me with information that shows you're also following the steps above.

If you fail to follow these guidelines, I will take legal actions against you and your website in the near future.

TERMS AND CONDITIONS
0. USED TERMS
MOD - modification, plugin, a piece of software that interfaces with the Minecraft client to extend, add, change or remove original capabilities.
MOJANG - Mojang AB
OWNER - shinoow, Original author(s) of the MOD. Under the copyright terms accepted when purchasing Minecraft (http://www.minecraft.net/copyright.jsp) the OWNER has full rights over their MOD despite use of MOJANG code.
USER - End user of the mod, person installing the mod.

1. LIABILITY
THIS MOD IS PROVIDED 'AS IS' WITH NO WARRANTIES, IMPLIED OR OTHERWISE. THE OWNER OF THIS MOD TAKES NO RESPONSIBILITY FOR ANY DAMAGES INCURRED FROM THE USE OF THIS MOD. THIS MOD ALTERS FUNDAMENTAL PARTS OF THE MINECRAFT GAME, PARTS OF MINECRAFT MAY NOT WORK WITH THIS MOD INSTALLED. ALL DAMAGES CAUSED FROM THE USE OR MISUSE OF THIS MOD FALL ON THE USER.

2. USE
Use of this MOD to be installed, manually or automatically, is given to the USER without restriction.

3. REDISTRIBUTION
This MOD may only be distributed where uploaded, mirrored, or otherwise linked to by the OWNER solely. All mirrors of this mod must have advance written permission from the OWNER. ANY attempts to make money off of this MOD (selling, selling modified versions, adfly, sharecash, etc.) are STRICTLY FORBIDDEN, and the OWNER may claim damages or take other action to rectify the situation. Read the redistribution rules for more information.

3.1 MODPACKS
You are allowed to include this MOD in a modpack, as long as you follow the modpack terms (found in the lower section of the post). As long as you follow the terms listed there, you are allowed to redistribute this MOD in said modpack.