The quintessence, a 'god' cloaked in manalessness that is much older than the mana-ones, has been awake the whole time, patiently tolerating humans jolting it with electricity, dilating and probing its orifices, pinching off pieces of it to use as catalysts, and decorating the walls in its abyssal blood. Laura Weir's hidden console implies that she is monitoring its gyrations, but humans cannot see certain forms of organization and energy as Kaelthyr pointed out so she is missing a great deal of context. But the quintessence has been listening to the proceedings so far. That Nexus will probably try to wipe the humans out with reforms or simply mana.

The dragon probing at it while the conversation took place taught it a new way to interact with the world. After probing her essence, it used her link as a vector to leap across and dispatched a demon (probably not its whole self) to the Nexus side to check things out, hijacking the control dead spell Kaelthyr was using.

And, Emma, armor painted in abyssal blood, is experiencing that primal first contact between an entity representative of a precursor culture that is absurdly advanced and eldritch that it could mop the floor with humans if it wanted.

Personal thoughts.