The Soul travels through “metempsychosis,” supposedly, and “transmigration,” where the Soul has many trials and transformations. In EC this too is really evolution, although it is devoid of materialism in the old religions.
The Kabbalists say (see the Kabbalah by Adolph Franck) that Souls alone lack the power to regain heaven so therefore they seek other Souls to unite with to complete each other, with each Soul looking for a more virtuous or stronger Soul. This is really evolutionary reproduction in ECC and this progression can develop into evolutionary advancement.
In ECC this transmigration is rather smoothly transformed and returned to evolution, reproduction and evolutionary advancement. In TC it is the Spirit which activates the Soul and Body to evolve to Godhood.