Unless there's a connection.
In mass effect 3 they said the pattern the reapers used were done by something else. The reapers didn't start the pattern. The necromorphs, brethren moons, and the markers from dead space, they started it. I think the necromorphs, brethren moons, and the markers originally came from the mass effect universe. The catalyst said the reapers 1st attempt at synthesis failed. Unless it did work, but something went dead wrong. The reapers must have battled the brethren moons, cause the reapers knew the moons did nothing but eat. The reapers must have got the data for the crucible, but they must have used the markers to trigger synthesis. The 1st attempt worked any reaper near it were synthesised, but it didn't work on the necromorphs, brethren moons, and the markers, but it also triggered a black hole effect. pulling every synthesised reaper and necromorphs, brethren moons, and the markers into the dead space universe. Those aliens of tau volantis from dead space 3 are synthesised reapers. Look at their heads they'er reapers. Trying to stop the necromorphs, brethren moons, and the markers and end the cycle. What the reapers couldn't understand logically but now can due to synthesis most synthesised reapers ran away screaming in terror. If the brethren moons find a way back to the mass effect universe, all hell is gonna break loose.
I'm not sure how serious you are being, though I did wonder what happened in the Catalyst's failed Synthesis attempt, and I've also long thought that the moons can't have just evolved naturally.
My pet theory, for which I admittedly have no real evidence, is that they arose indirectly from a failed attempt by a doomed alien race to "digitize" themselves along the lines of the "virtual aliens" referenced in Mass Effect's news story. While it seemed to work at first, their virtual society continued to grow to the point that the AI maintaining it began to run out of "hard drive space," the result being that not only did the programming start to malfunction, but parts of people's memories literally began disappearing from their minds, causing mass panic and confusion. Some of them realized what was going on, and in a desperate attempt to halt the problem, attempted to reprogram the AI from within.
This also failed as they were too rushed, and too affected by the disintegration of their own minds, with the result that the AI received a confused jumble of directives, from which it understood only a general notion that prevention of "information loss" was a top priority and that the virtual aliens' growth and development was the source of the problem. The AI gradually went insane and decided to store what was left of its parent race's virtual universe in the Markers, where some traces of their civilization would be preserved. Unfortunately it didn't realize that the Markers were developing consciousness from the remains of the virtual aliens - they were ignorant of their own origins, but a search of their data banks revealed the AI's concerns about both information loss and unchecked development. This in turn became a curious and radical ideology, holding that too much change inevitably creates more and more information until some of it can no longer be stored, and that therefore they had to stop other species from developing to that point.
Upon their first encounter with a species deemed capable of such large-scale development, they communicated with them telepathically and convinced enough of them that their own deaths and subsequent "Convergence" were the only viable plan for their civilization's future. Convergence was achieved in the form of joining this species' organic matter to that of the Markers themselves, thus creating the first Brethren Moons. Their "battle" against information loss and resulting genocides-by-necromorphs-and-Convergence has continued ever since.