Eden has two trees, the tree of knowledge of good…

Eden has two trees, the tree of knowledge of good and evil and the tree of life. If the tree of life meant to give eternal life, the tree of knowledge of good and evil is for what purpose it was planted there? Is it only for the test of obedience? In Revelations the tree of life is present but the other tree is absent. Does that mean that the tree of knowledge of good and evil is death? Every input is much appreciated!