To combine amusement from both flavor and mechanics, a Dark Pact Shadowthief would be fun. Kill things and build up two separate pools of energy harvested from them for different effects.Might be funny trying to build a Star pact shadowthief, then again the star pact base class feature is a lot weaker than the shadowthief's.
Need more bean-counting fun? Hybrid or multiclass with a Psionic class and manage power points too ^.^