The titular Castithan species is available should you wish to create a new character. Or feel free to change the species of your existing avatar if you'd rather. Trion has also added an instanced single-player horde mode option that ties into the new storyline. If you're playing on consoles, you've also got some new achievements and trophies to hunt.
The Castithan Charge Pack costs $9.99 on PCs and the PlayStation 3. Xbox 360 users will need 800 Microsoft points. Don't forget to check out the trailer after the cut.
[Source: Trion press release]