The third of three symbolic mountains that represent stages of spiritual development. The third mountain is a process of refinement in which the resurrected master (who died and resurrected at the end of the second mountain) perfects the consciousness in greater and great degrees. This is related to the trinity, the world of Atziluth, and the kayas described in Buddhism. In that world, there are no egos, defects, or impurities, only ascending degrees of perfection and wisdom.
"And a river went out of Eden" (Genesis 2:10) [means] that there are no strange Klipoth ["empty shells" ie. psychological defects, egos] in the Tree of Life above (in Atziluth), as it is written: "For thou art not a God (אל El) that hath pleasure in wickedness: neither shall evil dwell with thee." (Psalm 5:4), but in the tree below (in Briah) does indeed have strange Klipoth." - Zohar
"...remember the last supper of Our Lord Jesus Christ that died, after which he was buried and resurrected on the third day in the light of the eternal everlasting world. Learn, oh my son, that nothing can live until first it has died." - Raymond Lully, Calvicle (13th cent)
See "The Three Mountains" by Samael Aun Weor and What are the Three Mountains?