The living one (Revelation 1:18)
Your eternal life depends entirely on your relationship with Jesus Christ. John has just first seen Jesus in a vision and fell over as if he were dead. But Jesus laid his right hand on John, telling him to fear not. Jesus is the first and the last, Jesus said. He continues in verse 18,
and the living one. I died, and behold I am alive forevermore, and I have the keys of Death and Hades. (Revelation 1:18)
Jesus is alive. We place a heavy emphasis on the death of Christ, as we ought to. It's because of His death that sinners like you and me can be declared not guilty because, on the cross, Jesus took the punishment that we deserve. The cross is so central that in the city of Corinth, that's all the Apostle Paul preached--Christ and Him crucified (1 Corinthians 2:2).
With that said, we need to regularly remind ourselves that Jesus Christ is no longer dead. (That's partly why we worship with God's people on Sundays.) On the third day, He rose again. He had laid His life down on that Friday and picked it back up on that Sunday (John 10:17-18). He is "the living one."
He did die in our place but behold, He is alive forevermore. Related to His death and resurrection, we see that Jesus has the keys of Death and Hades. As the One who conquered death and the grave, He rules over both. He has the power to save, and He has the power to cast into hell.
Reader, your eternal life depends on your relationship to this living one. If you receive Him, if you trust in Him, you will be forgiven all of your sins and granted eternal life. But if you reject Him who has the keys of Death and Hades, then you will get what you rightly deserve--eternal death. Which will you choose on this day? The choice is clear. Give your life to the One who laid down His life for sinners like you and me.