What is a mod? Short for Modifications, mods are data files which, when loaded, can radically change the gameplay of Diablo. From new spells, new monsters, and new items, to faster, tougher, and smarter enemies, mods attempt to raise the difficulty of the game for all players and classes. Mods are for the PC only (there are no Macintosh mods).
What do you need to play a mod? Well, for starters, mods out there work for Diablo 1.07, not the latest version (1.09). So the first step is to download the 1.07 patch for Diablo and create a second Diablo folder by copying the contents of your current Diablo folder into a new one. Then apply the patch.
Start the game (Diablo or Hellfire) and load up DHACK, the program you use to load the DAT file of the mod. To do this, start up the game, task switch out (Alt-Tab), load up DHACK and activate the mod's DAT file, and you're all set (for solo play, that is).
Playing mods multiplayer is a little more tricky. Since Battle.Net will always attempt to upgrade your Diablo version to 1.09, you cannot play mods over Battle.Net. There are quite a few alternatives, though:
LAN play
Modem connection
Kali, a program which allows you to play Diablo over a virtual LAN ($20 one-time fee)
Here's a quick synopsis of the major (in other words, most popular) mods of Diablo and Hellfire. If you're thinking of playing a mod, this is a good starting point to decide which one is right for you. For more information on any mod (because the features I list are only a small fraction of what these mods bring to the table), I heartily recommend you visit the mod's homepage.
Features: With 90 new monsters, 22 new base items, 16 new suffixes, 6 new prefixes, 64 new unique items, and 6 new spells, Abysmal has a lot to offer. All monsters have beefed up stats. Many items have built-in powers to them. And for the challenge? As Tommi writes, "Hell/Hell is a place where you should go only when you've lots of powerful friends with ya... And while being powerful yourself too."
Features: Dr. Zed's mod has a number of features not in any other mod. Players can select character classes and races, affecting their stats, spells (based on type), and, depending on the race, their life/mana. Every unique in the game is new. Many new monsters are in the mix, and stat changes accompany every monster. Bows have arrows, not durability. Money is scarce. And the duping bug in Diablo has been fixed.
Author: Anon. Game: Hellfire v1.01 Download: Multiplayer and Single Player versions are separate. If you want to play both MP and SP, you'll need both versions.
Features: Uses the same characters as regular Hellfire. Fixes various left-over bugs and removes annoying/useless features. Allows all unique items to drop. Adds bosses in Crypt/Hive. Full readme
Features: Compatible with only multiplayer Hellfire: Fixed v1.21. Wirtistopheles "expansion" adds a new dungeon level to Hellfire: Fixed in the same manner as mods that use *.dat files. Full readme
Features: A mod based on Varaya and Khan's, Hellfire - The Dark is designed to balance the character classes more completely. Changing the attributes of the classes, and the prefixes and suffixes, its goal is to improve cooperative play.
Features: Netherworld has some neat features like no Chain Lightning gapping, Golem co-op (with hit point and owner displays), interesting prefixes and suffixes (one can raise the qlvl of monsters, improving their drops), and tough new monsters. Shrines act in interesting ways, and you can carry artifacts which act as portable shrines. Monster displays will show how many hit points a monster has left. Check it out.
Features: Like all mods, it features tougher monsters to overcome. New spells, items, and monsters are adorned all over the game, including the Hive and the Crypt. This was one of the earliest Hellfire mods and wasn't updated much.
Features: The name might be a gimmick, but the work gone into the design of the mod isn't. Every single monster, including bosses, and all uniques in the game are new. Changed base item attributes along with new prefixes and suffixes give a whole new look to item collecting. Mana Shield and Stone Curse don't exist to add to the challenge, and humor is thrown in to spice it up here and there.
Varaya and Khan's Mod
Authors:
and
Games: Diablo and Hellfire Mod: No longer hosted at their website
Features: the first mod ever made, V&K has continued to excel throughout its existence. The authors have a commitment to quality in the mod, and it shows. Probably the most popular mod out there, V&K (its pet name) has a list of features a mile long. It's also for both Diablo and Hellfire!
Features: Varaya and Khan have once again teamed up to make a mod based on Tolkien's Middle Earth universe. Including new graphics, making the mod quite large, it adds a lot of variety in gameplay simply because the whole theme of the game is changed. Every single unique in the game has been replaced. Bosses and monsters have been changed to reflect a Tolkien style.
How does one go about making a mod? It's no simple task. Mod Making programs do exist, but I'd classify them as buggy and crash-prone at best. Real mod making involves hex editing and assembly, for more complex changes. I'd also recommend a solid working knowledge of Jarulf's Guide, especially items and monsters. Jarulf's DView is also recommended if you'll be modding via exe (rather than dat file).
Features: Zamal and Zenda host the best Mod Making Tutorial that I know of, and a mod making forum as well. The workshop contains information on monsters, items, spells, shrines, characters, and more. Don't miss their DarkModNotes.zip at the bottom of the page. Selby.zip (within the zip archive) contains a catalogue of offsets for Hellfire monsters, items, and other things. Very handy.