Basically
Constant wakes up in the new worlds, gets beaten up, travels these worlds, finds characters both new and similar, and finds out that this army that has invaded many worlds might have a device that can stop the Singularity from collapsing and taking out all of reality, so he works to create a beacon that goes across as many worlds as it can to call an army so they can defeat them and get the device
He goes through a number of quests, meets all of the villains
That's all I got so far