Hello Jeff, thank you for the concern, question in regards to the keys? I am going to share a few other scriptures to help in your understanding.
Then, behold, the veil of the temple was torn in two from top to bottom; and the earth quaked, and the rocks were split, and the graves were opened; and many bodies of the saints who had fallen asleep were raised; and coming out of the graves after His resurrection, they went into the holy city and appeared to many.
Matthew 27:51-53 NKJV
I am He who lives, and was dead, and behold, I am alive forevermore. Amen. And I have the keys of Hades and of Death.
Revelation 1:18 NKJV
Therefore He says: “When He ascended on high, He led captivity captive, And gave gifts to men.” (Now this, “He ascended”—what does it mean but that He also first descended into the lower parts of the earth? He who descended is also the One who ascended far above all the heavens, that He might fill all things.)
Ephesians 4:8-10 NKJV
Verse 8 is an original testament quote from Psalm 68:18.
Scripture teaches both the mouth of two or three witnesses every word is established. Same goes with scripture when in many passages it shares a complete truth.
Pray this helps, ask another question after you check this our. Be more than happy am ready to help.