Amen; and have the keys of hell and of death. – Revelation 1:18

The mediatorial office which Christ now occupies is one of great power. He is “God over all, blessed for ever.” His dominion is over land and seas and over heaven and the regions of the dead. There is nothing hid from the energy of His power. He is Lord of all. “He hath the keys of hell and of death.” By the word “hell” may be meant here the entire invisible land, the whole realm of spirits: Christ is Lord there, adored in heaven and feared in hell. But, if we restrict the sense to the common meaning of the word in our language, He is Lord of hell. The devil despite his malignity can do nothing but what Christ permits him. He is a chained enemy; he may rave and rage, but he cannot injure the child of God. Christ hath him ever in check, and when He permits him to wander abroad, He makes the wrath of man and the wrath of devils to praise Him, and the remainder He doth restrain. Why dost thou fear therefore? Thou sayest, “I am a sinner-Satan will prevail against me.” But Christ saith “I am master of Satan, I am Lord of hell, he cannot prevail against thee.” He cannot leave hell unless Christ permits him, for Christ can turn the key and lock him in. He could not take thee there, for Christ has locked thee out and keeps the key. Thou art eternally and perpetually safe from all the machinations of the powers of darkness. And dost thou tremble at death? Is it that which alarms thee? Have the pains and groans and dying strifes sounded in thine ear till thou art timid and afraid? Then remember Christ hath the keys of death…Fear not, therefore, but remember that death is no longer death to the saints of God, they fall asleep in Jesus. ~ C.H. Spurgeon

https://www.blueletterbible.org/comm/spurgeon_charles/sermons/1028.cfm