If I was suffering, I could and would ask you, a fellow committed Christian with a personal relationship with Jesus Christ as my Lord and Savior. Likewise you could ask me for prayer. Paul recommends we pray and intercede for one another. That is intercessrory prayer.
Now if I were visiting you in your home, and you asked me in earnest to pray for your affliction, I would indeed do so. I would take it before the Lord Jesus Christ in prayer that very day.
Does death hold any power over you? Does death hold any power of me?
No.
We are both alive in Christ.
If as I left your home, I was killed in an accident, I am still alive in Christ, a fellow brother in the Lord. That human death holds no power over me.
As I come before the throne of Jesus christ, still alive in Jesus christ just as I was on earth, and just as you are now still, will I forget the pleading of my brother in Christ?
No.
I will take your needs before the Lord in Heaven.
Furthermore, I am still alive in Christ. You are still alive in Christ. Death still holds no power over either of us.
Because we are both still "saints" alive in Christ, we can both still pray for each other.
Furthermore, since death holds NO POWER over either of us, we can both still be brothers in Christ, we can both still be in communion with each other and with Christ.
Part of that communion in Christ is a continuation of our intercession for one another. I can still intercede for you. You can STILL ask me to intercede for you for we are both still brothers in Christ for whom death holds no power. Since in Heaven I exist outside the space and time of earth, there is no time as we know it on earth. Our life there is purely a participation in the life of the Holy Trinity and a sharing in the Beatific vision.
So if you alone come to me to ask my intercession in Heaven, as we are both still alive in Christ, I will indeed hear and answer you.
Furthermore, if a billion Christians come to me for intercession, in Heaven, outside the space and time of earth, dwelling in ETERNITY, I will have ETERNITY to hear and answer ALL those billions of requests for intercession.
That is, simply put, the whole basis for asking for the intercessory prayer of Mary. In all the lines above, susbtitute Mary for me. It is simple, biblical, and fundamentally Christian.
God's word also says that the dead cannot communicate with the living. Our only link beyond this world is the Holy Spirit, all other spirits are Antichrist, and are forbidden.