|Fury of the Tempest|
For each 3 paragraphs of background you gain additional perks: 1 - extra trait, 2 - extra feat, 3 - extra +2 to an ability score, 4 - gain a mount CR 3 or below, 5 - gain a crafting feat, 6 - gain a wish, 7 - gain a magical ring no more than 8,000 gp (You must write the description, abilities, and background of the ring in your crunch as well), 8 - gain a familar or animal companion, 9 - gain a super power, 10 - gain another 'Special' from another class.
30 paragaphs... godamn that's one heck of a challenge. Admittedly, the first 3 rewards are much, much stronger than the rest... at least until you get to number 9 and 10!
Honestly, I'm stunned you're making people play level 5 characters and asking for so much backstory! How the heck are we meant to write that much backstory when we're only level 5?