Felix understood that absorbing those two cores was nothing but a mere bonus...His goal was always to absorb their souls' explosion as he was certain that they would go for it even if they didn't take their cores with them.
That's because he had prepared a tight plan to imprison their souls here forever, leaving them with the sole option of self-implosion if they desired to leave his domain!
With their cores being safe in their territories, Zeus and Poseidon wouldn't hesitate to go for it.
"It's time for the last dance, the last act, and if I want to bring everything together, I can't make a single mistake," Felix uttered as he took a deep breath.
"We believe in you..." Thor encouraged with a solemn tone, recognizing the true difficulty of Felix's final act.
"Felix, you have gone through this so many times now." Lady Sphinx said as gazed at him with a faint smile, "The circumstances might change, but you always emerge victorious."