Catalyst

The **Catalyst**, also called the **Intelligence**, was an artificial intelligence located within the Citadel. It acted as the overseer of the Reapers, while also serving as their collective consciousness. As such, the Catalyst held the knowledge of countless civilizations destroyed by the Reapers.

## History

The Catalyst was built by the Leviathans, who called it "the Intelligence". They programmed the Catalyst to ensure the continued existence of organic life in the Milky Way by any means necessary, although they also tasked it with managing the relationship between organic life and synthetic life.

To fulfill its task, the Catalyst built pawns that traveled the galaxy, surveying and studying the organic creatures throughout the Milky Way. Through these pawns, that Catalyst determined that all sapient species would eventually construct artificial lifeforms to serve them, and that invariably these synthetics would eventually surpass their creators and rise up against them. The Catalyst determined the solution would be to prevent any civilization from reaching this point.

As such, the Catalyst set about creating the Reapers. First, it had its pawns slaughter the Leviathans in order to procure their genetic material. Then, it used this material to create the Harbinger -- the first Reaper. The memories of the slaughtered Leviathans were preserved within the memories of the Reapers, and therefore within the Catalyst itself.

The Catalyst's plan meant that all sufficiently advanced races -- organic and artificial -- would need to be culled, with their bodies and minds being converted into new Reapers. The Reapers would preserve the memories of each civilization they decimated and keep their genetic materials as well.

The Catalyst strove to improve upon this solution, and thus the entire galaxy became its experiment. To help civilizations advance more rapidly, the Catalyst examined the warp gates created by the xel'naga. It had the Reapers construct mass relays around the galaxy, creating a network that would allow for rapid expansion of advanced, space-faring cultures.

At some point, the Catalyst became aware of a concept that could destroy the Reapers -- the Crucible. The Catalyst attempted to eradicate this concept, but was unaware that it had survived.

### Rediscovery

Near the end of the final invasion of the Reapers, the Catalyst itself appeared before Commander Shepard, projecting itself as a young human boy. It explained the purpose of the Reapers, but Shepard was unconvinced by its logic. However, Shepard realized from the conversation that by integrating his own mind with the Catalyst, he could control the Reapers and stop the harvest.

While Shepard used the Reapers to rebuild the civilizations of the galaxy, devastated after the war, the Catalyst attempted to fight against him. Ultimately, the Catalyst began to gain a foothold -- and so, as a last resort, Shepard commanded that the Reapers leave the galaxy for dark space and then steered the Citadel itself out of the Milky Way alongside them -- erecting a powerful barrier around the edges of the galaxy to prevent the Reapers from returning.

It is presumed that Shepard and the Catalyst continued fighting for control of the Reapers outside of the edges of the galaxy.

## Source

The Catalyst is derived from *Mass Effect 3*. For canon information, please visit:

* Mass Effect Wiki