I've been reading the newly released Realms of Crawling Chaos all morning.
This ritual requires previously prepared essential saltes. The magic-user calls on the attention of Yog-Sothoth, and harnesses properties of time and space to bring back the dead from their essential saltes. The success of the revivification is completely dependent on the state of the body from which the saltes were prepared. If saltes are prepared from less than 51% of a body, the ritual will bring up an unidentifiable mass of flesh that only lives for moments.
[...] it should be noted that anytime an Outer One tank is found, the occupant will have no brain. The body is surgically altered to allow it to survive without the brain, but the brain may be in an altogether different galaxy or dimension.
There are some books that I admire but never use in play. Realms of Crawling Chaos isn't one of them. It's packed full of goodness that's easy to drop into any campaign. And the PDF is under $5. Go buy it!