"The Keys of Hades are magic "keys" owned by the god Hades."
https://riordan.fandom.com/wiki/Keys_of_Hades
"The gates of Haides were securely locked to prevent the escape of souls. Haides, or his doorman Aiakos, kept the golden keys."
https://www.theoi.com/Khthonios/HaidesTreasures.html
"interesting about this is that the Greek god Hadēs was occasionally depicted in Greek mythology as carrying a key to the gates of the underworld. He kept the gates forever locked so that nobody who was within could ever escape.
But in Revelation 1:18, we see that Jesus now carries the keys, and He plans to throw the gates of hadēs wide open."
https://redeeminggod.com/hades-hell/
"In this Scripture, Jesus is declaring his authority over death and hell (Hades), by implying that the keys to the aforementioned, which once belonged to another, are now in His possession."
https://www.christianity.com/wiki/heaven-and-hell/did-jesus-fight-satan-for-the-keys-to-death-and-hell.html
"Since Christ alone has conquered death and has Himself come out of grave, He alone can determine who will enter death and Hades and who will come out. He has the "keys." He has authority over death and the place of the dead.
Satan has never possessed these "keys." Satan has never had power to determine who goes to Heaven (the Kingdom) and who goes to Hell."
https://www.gotquestions.org/keys-to-the-kingdom.html