SRD:Astral Seed

This power weaves strands of astral ectoplasm into a crystal containing the seed of your living mind (hardness 1 and 1 hit point). You can have only one astral seed in existence at any one time. Until such time as you perish, the astral seed (also called the storage crystal) is utterly inert. If you are slain at some later date, your soul transfers into the storage crystal, which begins to dimly glow.

Upon transference, your physical remains (should they still exist) become inert matter and cannot thereafter be restored to life. The transfer from the slain body to the astral seed works over any distance, physical or extradimensional.

Once your body’s physical demise activates the storage crystal, you have the abilities of a psicrystal of the appropriate level, plus all the powers you knew and the maximum power points you possessed when astral seed was manifested—but you also have a negative level that cannot be healed and that does not convert to real level loss in your current crystalline form. You have thirty days to grow an organic body, after which time your sentience fades and your soul passes on if it hasn’t entered a new body.

To grow a body, you (in the storage crystal) must spend ten days in uninterrupted solitude. The body’s constituent parts are pulled as ectoplasm from the Astral Plane, then slowly molded and transformed into a living, breathing body that is an exact duplicate of your body at the time you manifested astral seed (the crystal itself breaks down and becomes a part of the new organic body). When the tenth day ends, you completely and totally inhabit the new body. You possess all the abilities you possessed when astral seed was manifested, at one level lower, but you have none of your equipment.

If the body is struck for any amount of damage during the ten-day period when it is growing, it is destroyed and your soul passes on.

Conceivably, you could manifest mind switch to utilize a temporary body, but only an evil creature would smash his own temporarily empty storage crystal to permanently usurp a subject’s organic body (unless the subject is itself irredeemably evil).