There was no one on the Mercy Seat.   

When Christ Jesus (who was begotten by the Holy Spirit) fulfilled His purpose, He was qualified to extend mercy to all.   

So, it is Christ Jesus who sits upon the Mercy Seat (the Holy Spirit) which is now the Throne Of Grace.   

Mercy has been fully extended and now unmerited favor is available to as many as receive Christ Jesus as Saviour and Lord.   

For the Holy Spirit so loved the world, that he gave his only begotten Son, that whoever believes in him should not perish, but have everlasting life. Joh 3:16 The Holy Spirit is the eternal, omniscient, omnipresent, omnipotent Creator of all things by the Word.      What world is John speaking of?      The earth and all the people born into humanity.      The Holy Spirit is love and love is of the Holy Spirit.      The world was created by the Lord and it is good.     We know that man chose rebellion against the Lord and so humanity became evil.     But the Lord loves the people of this world and so He birthed Christ Jesus into the world to redeem it and us.      Love is what led the Holy Spirit to be born as a human, to suffer and die for us.      The Gospel is heard and those who are hungry are lead by the Holy Spirit to believe and receive the Truth.      The Truth sets us free from sin, from death and hell and brings us to Eternal Life by the infilling of the Holy Spirit.      Here is understanding:    → Everlasting Life is Eternal Life    → Eternal Life is union with the Holy Spirit.

For the Holy Spirit sent not his Son into the world to condemn the world; but that the world through him might be saved. Joh 3:17 Condemnation is of Satan.     He tempted Eve to cause her to fall into condemnation.     He is our accuser.     He hates humanity.      But the Lord loves us and desires for us to be saved - to experience eternal, abundant life.

And the Holy Spirit and the bride say, Come.     And let him that hears say, Come.     And let him that is athirst come.     And whoever will, let him take the water of life freely. Rev 22:17 A final call to those who have not hardened their hearts to His love and Grace.     The Water Of Life is the Holy Spirit of the Lord who is given freely to whosoever asks.      Note that is is the Holy Spirit of Christ Jesus and His followers that extend the invitation to come to Christ Jesus and live.         → We preach the Gospel    → the Holy Spirit draws believers to Himself.