It's been a while since this game came out, about a year I think.
The two new character classes in Lord of Destruction are the Assassin and the Druid. There are two new types of insertable items, Runes and Jewels, and a new kind of item called Charms. I also think the last Act's quest rewards are worth mentioning as well.
- The Druid
The Druid is, like the Paladin, a sort of hybrid of a spellcaster and a melee fighter. Unlike the Paladin, however, the Druid's spells are rather diverse: on one tab he has Sorceress-like elemental spells, on another he has Necromancer-like summoning spells, and on the last he has Paladin-like combat skills - with a twist.
The elemental spells are varied in type - the Druid has a couple of fire spells, and an ice spell called Arctic Blast which is basically an ice Inferno. He also has a couple of interesting wind spells that work like the Death Knight's Whirlwind in Warcraft II. That is, they wander around the screen, damaging whatever they touch.
The summoning skills are a little different than the Necromancer's. The first summoning skill you can use is called Raven, and creates a raven that hovers around you and attacks a set number of times - I forget what it is exactly. Aside from that Ravens work similarly to Skeletons. Then, there are Spirits, Wolves, and eventually a Grizzly. There are various kinds of Spirit, and they are basically summoned units that have auras like the Paladin's. There are two kinds of Wolf, and you can only have up to three Wolves at a time. Finally, there is the Summon Grizzly spell. It summons a huge bear. You can only have one bear at a time, but it is extraordinarily strong.
And then there are the combat skills. These skills have a twist - you must first turn into a Werewolf or Werebear to use them. A Werewolf is faster and has a better rate of attack than a regular Druid, and the Werebear is bigger, has a heavier attack, and more HP.
Druids have another interesting facet: they get a fast attack rate with Mauls.
- The Assassin
The first thing that you should know about Assassins is that they have an entire weapon class devoted to them: Claws. An Assassin can use two Claw-class weapons at once, which initally gives them the same attack capability as a Barbarian, with a much faster rate of attack.
Assassins have two new kinds of skill: Martial Arts and Traps. Each time you use a Martial Arts skill, it puts a charge on the affected enemy. If you use a "Finishing Move," the charges get turned into attack bonuses.
One of the first Trap skills is basically a hand grenade, and the other is a patch of lightning that sits on the ground for a small period of time. There are also a couple of blade Traps that are basically throwing stars. However, the higher-level Traps are small objects that act like the Sorceress' Hydra. The level-30 Trap is called the "Death Sentry." If you liked the Necromancer's Corpse Explosion, you'll love Death Sentry. Whenever a monster goes near the Death Sentry, it starts exploding nearby corpses until the monster leaves the area or dies.
There is also a tree of skills that give your claws elemental attack bonuses, and two skills that summon shadow warriors - basically mirror Assassins.
- Runes and Jewels
One of the coolest new features of Diablo II was the Gem. In LoD, there are two new kinds of items you can put in a socketed item. Jewels are like Magic items: you must identify them before you can use them, and they have one or two random attributes. (There are, however, Rare Jewels, although I've yet to see one.)
Runes are a unique kind of item. There are quite a few kinds of Rune - 20 or so. Each kind of Rune has a different effect, similar to the different kinds of Gem. However, the Runes have a variety of different effects, such as increasing light radius, or making the item indestructible. By Transmuting three of the same kind of Rune in the Horadric Cube, you can get one Rune of the next higher level. And if you put the right combination of Runes in the right class of Socketed Item, you get a Runeword, which is more or less a quick and easy path to a Unique Item, and one whose power you can define to a point. (Elite items are great. Elite Runeword items are greater.)
- Charms
A Charm is a magical item that, once identified, need only be carried in your inventory and you get some sort of bonus.
Charms present a unique dilemma. There are three sizes of Charm: small charms, which take up one inventory slot, large charms, which take up two slots, and grand charms, which take up three. Naturally, grand charms carry the most potent benefits. However, it doesn't take long before you've filled half of your inventory with Charms. Charms can make your character much more powerful with very little effort, but they can also decrease your carrying capacity drastically.
- Act V Quest Rewards
Diablo II already let you Imbue items. This is very frustrating (like when you Imbue some lame Act I weapon, then get to Act IV and find some kick-ass second-level item (i.e. 30-something defense Sharkskin Gloves).
Well, in Act V, you can do two really cool things to your items: Socket them, and Personalize them. After completing one quest, you can take an item and add sockets to it. (How many sockets you get depends on the item.) Now let's say you find a unique shield. It has amazing bonuses, but only a little defense. It's carried you into Act V, but you really need more defense. So socket it, then put a Perfect Amethyst or high-level Rune in it.
Perhaps it's a small thing, but you can also Personalize your items as well. This puts your character's name in front of the item's name. For example "Swordback Hold" becomes "Corsicus' Swordback Hold."
- Other Changes
The Stash is more than twice as big. This needed to happen.
There are a shitload of new item attributes.
There are new rare and unique items.
Some of the old skills have been tweaked a little (some spells come with a cooldown period, for instance).
Hirelings follow you from one act to another. They have stats and gain levels, and you can actually give them equipment. You can also resurrect them if they die.
- In closing...
If you don't hate Diablo-style games, buy Diablo II and Lord of Destruction. Now.
Also, because of the new item attributes, it is a very good idea to start playing with the expansion. The bigger Stash alone makes the game so much more enjoyable.
And one more thing: Do not play this game if you want to sleep. In fact, you will have more success with it if you forgo sleep. Mountain Dew and coffee aid in that aspect.