Server attacks, restarts, and long lines for players logging in marred the launch of the latest World of Warcraft expansion pack early Thursday.

Blizzard Entertainment’s servers staggered under everything from unanticipated quest choke points to a Dedicated Denial of Service attack, as millions of players all attempted to log on and complete the same quests at the same time. Warlords of Draenor is the fifth expansion pack to the popular massively multiplayer PC online game, which has 7.4 million monthly subscribers.

“We’re excited to finally launch Warlords of Draenor and explore this new world with you, but we know that the experience has been less than ideal as we approach our first full day of launch,” community manager Micah Whipple (aka Bashiok) wrote in a forum post to players he kept updated with server news. “Thank you for your zeal to face down the tyranny of the Iron Horde –and for your continued patience as we work to improve the current experience.”

The problems, he wrote, came from a variety of causes, some of which the earlier launch time in Europe exposed. A DDoS attack targeted the company’s servers, adding to other issues in-game that were already causing player delays, he said. The company was making hotfixes and posting them as late as this morning.

Delays and lag at MMO expansion launches aren’t unusual, as more players than will ever normally hit the game at once log in to see what’s new. But the DDoS attack and design of two early quests dramatically increased the already stunning server load.

At first, everyone who wanted to play the expansion had to speak to a single character, resulting in a mad jam for those who wanted to pass through the portal to Draenor. Blizzard fixed that before the North American launch by adding a copy of the wizard Khadgar to major capital cities and making it impossible to ride mounts near him (so that these couldn’t cover him up).

(Fun fact: Khadgar’s flavor text in a later quest is “I can’t be everywhere at once.”)

Then once inside the new areas, Horde faction players couldn’t complete a crucial early quest: The creation of their new garrisons, the player-owned cities that form the hub of much of the expansion pack’s gameplay. The quest called for players to click on a surveyor’s leveling tool to see the completion of their new garrisons happen.

Unfortunately, the tool was small, and the pileup of players was enormous, and both combined with lag created a situation where the quest couldn’t finish. But because the garrison was the hub for the next few quests, the problem made it difficult for players to advance.

This problem received a hotfix within hours so that any player passing within a short distance of the tool completed the quest.

In some ways, the first 24 hours of World of Warcraft’s new expansion felt like a game of Whac-a-Mole. Players would expose a problem, and Blizzard would move swiftly to fix it, sometimes in minutes.

“Here are some of the other important issues we’re currently working to address,” Whipple wrote early on as players raged in the game’s forums.

  • “Instance servers timing out, which may impact dungeon access.
  • “Continent server issues, which are resulting in Player Not Found and disconnection issues.
  • “Garrison server issues, which are resulting in phasing and performance issues.”

Traffic was huge. Servers that hadn’t seen a login line for years had a half-hour wait as millions attempted to play. On Thursday night, in response to the increasing lag caused by the new crowd of players coming home for the weekend, Blizzard cut the number of players per server, increasing those lines to hours for some more-busy realms.

This morning at 5 a.m. Pacific, Blizzard took servers down for six hours of maintenance and updates.