As for the aspect chambers of the magic related aspects? They need to create, perform, experiment, on those aspect chambers, to create something or solve problems. Depending on what their aspect is or what problem they are facing.
On every floor of the aspect chambers there will be a new Nexus core added with the same gas like mana. So a second phase Seeker in that sense should have 4 nexus cores in total. The surface chamber will have 2 floors and underground chamber will also have 2 floors then, having one Nexus core on each floor making it a total of 4 nexus cores.
Another issue to keep in mind is that to advance to the next phase as a Seeker, you first need to complete the challenges of the last floor in both your aspect chambers. Only then, by accomplishing a certain amount of achievement, the world Will shall help you convert all the nexus cores' crystalline energies to the next state.
But there are other complications here as well, let's say someone has the aspects,
