Deuteronomy 18:10 There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch, 11 Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer. 12 For all that do these things are an abomination unto the LORD: and because of these abominations the LORD thy God doth drive them out from before thee.
That's good. Please don't engage in any of the listed activities, and we promise we won't either. All of them are explicitly condemned by our faith anyway.
There shall not be found among you any one that maketh his son or his daughter to pass through the fire, or that useth divination, or an observer of times, or an enchanter, or a witch, 11 Or a charmer, or a consulter with familiar spirits, or a wizard, or a necromancer.
It's very clear in this passage that God is referring to conjuring up the dead - such as in a seance. There's a big difference between seeking information from the dead and asking the saints in heaven to pray for us. In fact, God has not forbidden this, because he at times has given it—for example, when he had Moses and Elijah appear with Christ to the disciples on the Mount of Transfiguration (Matt. 17:3).
The Bible directs us to invoke those in heaven and ask them to pray with us. Thus in Psalms 103, we pray, "Bless the Lord, O you his angels, you mighty ones who do his word, hearkening to the voice of his word! Bless the Lord, all his hosts, his ministers that do his will!" (Ps. 103:20-21). And in Psalms 148 we pray, "Praise the Lord! Praise the Lord from the heavens, praise him in the heights! Praise him, all his angels, praise him, all his host!" (Ps. 148:1-2).
Not only do those in heaven pray with us, they also pray for us. In the book of Revelation, we read: "[An] angel came and stood at the altar [in heaven] with a golden censer; and he was given much incense to mingle with the prayers of all the saints upon the golden altar before the throne; and the smoke of the incense rose with the prayers of the saints from the hand of the angel before God" (Rev. 8:3-4).
And those in heaven who offer to God our prayers aren’t just angels, but humans as well. John sees that "the twenty-four elders [the leaders of the people of God in heaven] fell down before the Lamb, each holding a harp, and with golden bowls full of incense, which are the prayers of the saints" (Rev. 5:8). The simple fact is, as this passage shows: The saints in heaven offer to God the prayers of the saints on earth.
Somehow I don’t think that Jesus would consider His mother, who he revered above all women, or John, the youngest of his disciples, who he loved like a brother, and in whose care He left His mother when He died on the Cross, anything like what your selected bit of Old Testament scripture described.