Aster of course noticed that Eris was a bit out of breath after finishing engraving the yang chain link, and it was justified what she just did actually required one to be a Soul King, or Queen in her case.
For the simple reason that the yang chain link was an Immortal grade treasure, temporal engraved runes weren't hard to do for Eris even in her weakened state, where her soul energy reserves aren't even at the Spirit Trial realm.
Meaning that to achieve a momentaneous Soul Queen level, she has to use all her reserves in a single go, resulting in her feeling a bit drowsy.
Naturally, just like Mylene, she has her ways to draw out as much power as possible, which in her case means using her Genesis Core as a power source for a devastating attack.