Posted on November 10, 2022 in Technology

Corrupted Blood: Art Imitates Life

The heydays of online role-playing games came with a number of new social and digital interactions that would have never had an opportunity to occur before the internet. For example, the Falador Massacre in RuneScape (named for the in-game town the chaos first started in) ended up permanently changing the way the developers handled banning users as well as ‘checks’ for stat effects. How?

Things that game developers could never anticipate or fully test in a Beta environment only surface after real human gamers get their hands into the game. The Falador Massacre, for example, only happened because a server that was packed completely full of people lagged at a critical moment – and a couple of players had been fighting in the only place you could fight in a house (or in a town), the dungeon. The game failed to wipe their status (which was PvP enabled, or ‘Player vs. Player’ meaning the player is allowed to cause damage to other players in-game) and so they were able to fight people in an otherwise PvP disabled zone, leading to one of the most infamous video game moments of all time.

Corrupted Blood is another such incident – without real people pushing the game to it’s limit, these things can’t be found ahead of time.

WoW, Corrupted Blood for Free?

World of Warcraft is an online role-playing game where you can fight both game-generated and real players. Make friends! Make enemies! It’s up to you! You have the ability to ‘raid’ a boss with a group of other people if you so choose, but you don’t actually have to stay and fight the boss if you realize it’s above your skill level. You won’t get loot if you leave, but you won’t get loot if you die, either. World of Warcraft introduced a new expansion to their map as well as a new boss to go with it in the fall of 2005. Part of the boss’s gimmick was a debuff known as Corrupted Blood – debuffs are in-game effects that lower a character’s stats, whether that be health, speed, attack strength, etc. and Corrupted Blood would only expire/deactivate if the player defeated the boss or if they left the region. It was meant to spread to party members in close proximity, as it was designed after a disease, and it was actually intended to kill the boss later in the fight (he’d infect himself with it after trying to drink the player’s blood, and the debuff would make him much easier to kill).

However, there were a couple of issues that playtesters couldn’t have possibly discovered on their own. Corrupted Blood could infect in-game pets, firstly, but instead of just letting the pets exist in their debuffed state, players would put them into pet storage so they didn’t die during the fight. This put them into stasis, and basically saved them exactly as they were when they went into storage. Much like in the Falador Massacre, this created a loophole where the stat effect wasn’t erased, and so even if the boss died while the pet was in storage, or the pet itself was no longer in the new area, the pet still had Corrupted Blood as far as the game was concerned.

Secondly, players had fast-travel, which works like teleportation. They’d beat the boss (or quit the fight) and fast travel to another zone or town. Without physically crossing the in-game border, the game didn’t seem to realize the player had left the new region, and so they’d still be infected with Corrupted Blood in that case as well. This led to Corrupted Blood spreading to everyone in the vicinity of the fast traveller, including NPCs (non-playable characters, like shopkeepers and such) and other people’s pets. Maybe traveling to the new area and then back without fast traveling could have fixed it, but the NPCs can’t do that, players who don’t have the equipment to enter PvP zones and survive couldn’t do that, etc. and so Corrupted Blood spread like wildfire.

Fixing It

How did they fix it? The problem got so bad so quickly that WoW ended up rolling back the servers to before Corrupted Blood was released. They couldn’t get it under control, and even if they were able to fix the glitch that caused the wild spread right away, they’d still have to deal with all of the people, pets, and NPCs already infected. It was much easier to go back in time than fix it in the timeline the bug had created.

This actually caught the attention of more than one infectious disease expert in the process. Many infectious diseases and pandemics are studied using real data or mathematical models, but they don’t take into account the unpredictability of human behavior. By studying the Corrupted Blood incident, where real people did things like fast-travel again to try and fix the bug, or spread the debuff deliberately by going into areas with a lot of players, they had a slightly better idea of how a real pandemic might play out if it hit without warning.