In unlocking the Phoenix Force, Thanos' son Thane learned the secret truth behind Marvel's ultimate power, as the cosmic entity chooses death and rebirth over pure power. In Thanos #6 by Marvel Comics, the living embodiment of Death reveals that for the Phoenix to rise and Thane gains its incredible capabilities, there must be first «death» followed by «rebirth.» The idea that the Phoenix desires those over pure power is followed up when Echo eventually wields the amazing force herself.
The Phoenix Force is millions of years old and had many hosts over its lifespan, as the nexus of all psychic energy in the Multiverse has remained a constant throughout the Marvel Universe. As a result, the Phoenix Force has attached itself to the likes of Jean Grey, Firehair from the Avengers of 1,000,000 B.C., and several other heroes over time. However, when Thanos' son Thane, and later Echo of the Avengers, gained incredible power and became the new hosts of the Phoenix Force, they unlocked the secret about its true desires.
Related: Thanos' Return From Death Is Bad News For The Marvel Universe
In Thanos #6 by Jeff Lemire, Mike Deodato Jr., Frank Martin, and VC's Clayton Cowles from Marvel Comics, Thane's plan to use the Phoenix Egg to harness the powers of the Phoenix Force seems to have failed after Nebula kills him before he can bond with it. However, Death reveals that the only way Thane could have accessed the Phoenix Force was through «death and rebirth,» allowing Thanos' son to be reborn with the universe-shattering power.
The secret that the Phoenix Force requires death and rebirth and not pure power from its hosts ended up playing a key role in the hero Echo gaining its capabilities during the Avengers' Phoenix Tournament.
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