These phrases you are creating, are not swear words per se.
They are known as oaths or curses (not magical) in fantasy... They are not generally to insult someone, but used when angry about something, or taken by surprise.
The Baldur\'s Gate games were full of them, as are most fantasy books. They usually relate to some religion as already stated, and often consist of the races\' God and an item of theirs, or some more general aspect.
\"By Moradin\'s Hammer!\" Is from BG, a dwarven Oath.
\"Sithspawn, and Emperor\'s Black Bones\" are curses from Star Wars.
I read a book that infringed heavily on the christian religion... and their curse was \"s\'Bloody tree\" or \"Aedin\'s Beard\" or \"Aedin\'s Bloody Tree\"
I think we should keep modern, common insults out of this.
I like the Trepor, Pterosaur and Crystal related ones, as well as the Laanx and Talad ones...
\"Lanx\'s Mask!\" could be used when startled.