Ok, referring to my general reference for all thing Jewish and mystical[1], we have 4 universes each corresponding to an aspect of the creative act (the book isn't very detailed on how this works):
Atzilut, Beriyah, Yetzirah, Asiyah.
Each has its own tree of life; Malkhut for the next one up stands above Rachamin (Mercy), also known as Tiferet (Beauty), of the one below.
Further to some discussion months ago linking Severian with Gevurah (Strength, representing strict and unforgiving justice, tempered in the divine by the other sephira), it is also (apparantly) associated with the Old Testament figure Isaac.
I doubt this makes things any clearer.
Iorwerth
[1] The 'Ars Magica' RPG supplement 'Kabbalah: Mythic Judaism'. Not, perhaps, the most authoritative source, but most books in the game line are fairly well researched; best take this with a pinch of salt.