Multiplayer can be played with two to eight players (in even numbers), with any number of them controlled by the computer. Be careful though, the computer is quite good at winning. It'll sneak up on you while you're busy attacking your friends if you're not careful. You can choose a free for all with everyone against each other or you can break up into teams and work together. Given all the choices of troop types available, multiplayer is really very robust. In
Chaos Rising, they have introduced the Chaos races for you to play as in multiplayer. They're a really nice addition to the cast that was not available in the previous games. Each of the new characters have their own unique abilities. It will take you a bit to get used to all these different abilities, but some of them are really powerful so you should test out everything at least a few times and every character several times as well!
You probably would like to know a bit about the new characters that you can use now too. The Chaos Space Marines incude Chaos Lord, Plague Champion, and Chaos Sorceror. Chaos Lord is your strong attacking player. He's the "tank" character that you just run into a huge group of enemies and start slaughtering. Personally, I like the powerhouse characters. Plague Champion is the defense character. He's good for standing outside the battle and healing your allies. The Chaos Sorceror is a more balanced, multipurpose character. I found him to be a lot of fun as well. He can handle the melee if necessary and he can also cast some very powerful spells as well. I think of the new characters, I liked him the most, but it does take some time to get the hang of using his spells! Along with these characters, you also get Chaos Units, vehicles, and Daemons, so that's a whole lot of new items for you! In addition to all this, there are five new multiplayer units. The Librarian joins the Space Marines. He is a very powerful spellcaster, so you're really going to like having him available. There's also a new Ork, Eldar, and two new Tyranids.