My guess is, if his brain is absorbed into the Marker in an emotionally strong, stable state, he might be able to control the Moon himself (since he is the creator of it) and prevent the Moons from feeding on other life, or even kill the Moon or other Moons himself. Why does it need his brain to be absorbed? Who knows. Once he has done that, the Marker can no longer control him as well so the Marker “dies”, because it can no longer absorb its creator. And so in the final battle Isaac must finally “kill” Nicole, in other words forgive himself for everything and move on, defeating those emotions of guilt and sadness. The Marker is using Nicole’s death to control Isaac the fact that Isaac has feelings of guilt and sadness towards her death means that he and his mind is vulnerable and in a more fragile state: perfect for the Marker to use to control him better.

Which is why the final “boss” takes place in his head with Nicole.

It probably needed his brain and intelligence to complete its formation.īut, it didn’t just need his brain. The reason it didn’t form in DS2 is because it needed Isaac to join it, since he created it.

So the Marker is within this newly formed Moon. Brethren moons form with enough biomass once enough dead biomass has been collected, it gets attracted to the Marker in a Convergence Event - along with chunks of rock and debris - to form a Moon.

Brethren moon from dead space