Use of -se- when the first word ends with -s

I wanted to name something Blood of Dragonkind and decided on the compound name "Sossediiv." However, after rereading it and learning more from this site, I realized Sos could be read as "Sosse," Bloods, due to the rule of adding -e to make a word plural.

So what is the rule when it comes to using "se" alongside a word ending in "-s"?

Category: Grammar