2. 'pi' indicates a unit block within a string of modifiers, a break in the left grouping of each successive word. It is not a possessive marker. It cannot be followed by just one word (obviously).
IMHO, it is not so obvious. To me, "pi" is a disambiguation operator meaning something like "of". It is very useful to distinguish a property and a field of application.
jan sewi soweli is an animal god like egyptian one (soweli is a property)
jan sewi pi soweli is the god of the animals (soweli is a field of application)
we can cope to the rule by adding qualificatives :
jan sewi pi soweli ali
but this is not as minimalist as I'd like it to be.