Mistakes of the Past

The main theme of the campaign is a redemption story of the wizard Kazakus. I want all the characters so have some kind of past mistakes or dealings that they will catch up with them. I am using PH, Volo's, EE, DFC5ER, some UA, and some homebrew rules. The campaign is 40% combat/ 40% Role playing/ 20% Exploration. I love story telling and appreciate good character backstory. The party is currently trapped in a undead town and slowing becoming zombies themselves. PVP is not allowed and the tone of the campaign leans more towards good than evil but any alignment will be accepted as long as it will not create too much conflict with the current party. This is a group game.